Cosmology & Space Exploration

Newton’s 3rd Law on the ISS

Lockerbie Academy’s Faulkes Telescope Pictures Some of Lockerbie Academy’s Faulkes Telescope pictures taken by students in the school from 2007.

Here are the posters produced by N5 (2016-2017) They answer the questions posed in the research task document below which was created from the Full Content Check 2016. Check them out. There are still a few to come and some need to be updated. If yours isn’t here then let me know and we’ll update.

research tasks as a pdf file

research tasks as a doc file

Continuous Spectra2

Space Exploration Physics

(they’ll take some time to upload so be patient!)

Thermal protection systems

Satellite Periods

Effects of Cosmic Radiation

Risks benefits

Light Year

Observable Universe

Risks with Manned Space Exploration

spectra

Understanding of Space

Gravity Assist

In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist manoeuvre, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft. This saves fuel, time, and expense. Gravity assistance can be used to increase or decrease its speed or redirect the path of a spacecraft. The “assist” is provided by the motion of the gravitating body as it pulls on the spacecraft. It was used by interplanetary probes from Mariner 10 onwards, including the two Voyager probes’ notable flybys of Jupiter and Saturn.

A gravity assist around a planet changes a spacecraft’s velocity (relative to the Sun) by entering and leaving the gravitational field of a planet. The spacecraft’s speed increases as it approaches the planet and decreases while escaping its gravitational pull. Because the planet orbits the sun, the spacecraft is affected by this motion during the manoeuver. To increase speed, the spacecraft flies with the movement of the planet (taking a small amount of the planet’s orbital energy); to decrease speed, the spacecraft flies against the movement of the planet. The sum of the kinetic energies of both bodies remains constant.

Gravity Assist

Open Ended Space Question

  1. From your knowledge of energy, what might a space exploration scientist consider when sending a machine to land safely on an extra terrestrial body? The machine must be capable of sending back some intelligible data
  2. Two people are discussing satellite motion one person says:
    “Satellites stay in motion because there is no gravity”
    Using your knowledge of Physics comment on that response.
  3. An astronaut on the international space station was quoted as saying:
    “I sometimes feel like a human cannon ball.”
    Using your knowledge of physics explain why he is like a cannon ball in space.
  4. Recently Voyager 1, one of the first space probes launched by NASA in 1977, has now left our Solar System.
By Voyager_Path.jpg: created by NASAderivative work: Hazmat2 (talk) – Original from http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2143This file was derived fromVoyager Path.jpg:, Public Domain, https://commons.wikimedia.org/w/index.php?curid=18049439

EITHER: Using your knowledge of physics, explain how this space probe was able to reach the outer planets.

OR: Using your knowledge of physics, explain how NASA might know that the probe has now left our Solar System.

OR: Using your knowledge of physics, comment on what happens next to this space probe.

5. A daytime newsreader commented that, “Looking at the stars is like looking back in time.” Use your knowledge of physics to comment on the journalist’s statement.

6. There are many parts of space that are detected by different types of telescope. Use your knowledge of physics to describe one telescope that is used in astronomy.

7. A ball rolls off from a table as shown.

Use your knowledge of physics to comment on what the ball’s horizontal distance from the edge of the table would and would not depend on.

8. A velocity-time graph of skydiver 1 is shown below

 

A velocity-time graph of skydiver 2is shown below

 Use your knowledge of physics to explain how the second skydiver’s velocity-time graph during descent compares with that of the first skydiver.

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Mass, Weight and Weightlessness

Below is a link to an excellent website for you to check your learning about weight and weightlessness. It is probably just above N5 standard, so read through it slowly and carefully and ask if there is material you don’t understand.

http://www.physicsclassroom.com/class/circles/Lesson-4/Weightlessness-in-Orbit

How does ‘g’ change with height above the surface of the Earth?

Continue reading “Mass, Weight and Weightlessness”

Definitions for Space

These are some very basic definitions for the Space Topic

Universe: Sum total of everything that exists.
Galaxy: A basic building block of the universe that includes stars, star clusters, clouds of gas, dust and interstellar molecules.
Solar System: Is one or more suns surrounded by orbiting planets. Our solar system is composed of the sun, 9 known planets and at least 44 moons, thousands of “minor planets” (asteroids) meteors and perhaps billions of comets.
Sun: Dominant member of a solar system accounts 99% of the mass of the solar system. The sun is a giant star it produces heat and light. A big ball of plasma
Star: Principle components of galaxies. Living stars emit radiation across the electromagnetic spectrum.  Peak depends on the heat of the surface.
Planet: A relatively large body rotating in an elliptical orbit around a sun.
Moon: A natural satellite of a planet i.e. rotates around a planet. Moons do not produce their own light.
Mass: Mass is a measure of the amount of matter in an object. It is measured in kilograms. Wherever you go your mass stays the same.
Weight: Weight is the force of gravity acting on an object pulling it towards the centre of the Earth or any other large mass. Weight is a force and so is measured in Newtons. The weight of an object varies depending on where you are (which planet etc and how far you are from it’s surface, the further away from the surface the smaller is your weight)..
gravitational field strength : gravitational field strength, g, is the weight per unit mass. It is measured in Newtons per kilogram. It is the force of gravity or pull on each kilogram of mass.
Inertia: Inertia is the property of an object which makes it hard to get an object to move, or to stop a moving object. Inertia varies with mass, so the bigger your mass the bigger your inertia..
Acceleration due to gravity: All objects will acceleration due to gravity. On the Earth, close to the surface objects accelerate at 9.8 ms-2 .
Light year: The distance light travels in a year equivalent to 9.46 .
Light

Light does not travel at an infinite speed. It takes time to travel. It is so fast that we do not usually notice, although out in space the distances involved are so big that light takes a reasonable amount of time to reach us.

Light travels at: 3 × 108 ms -1

Given that it takes 8 minutes for light to get from the sun, how far is it away is it from the Earth?

8 × 60  = number of seconds in minutes  = 480s

Each second light travels 3 × 108m

d= v t

d= 3 × 108   × 480  = 1.44 ×1011m

How far does light travel in one year?

1 year  = 365days

365days  × 24 = 8760 hours

8760 ×60 × 60  = 31536000s in one year

Distance travelled in 1 year, d = v t

d = 3 × 108 × 31536000     = 9.46 × 1015 m in one year = one light year

The light year (ly) is the distance light travels in one year.

Light travels at 3 × 108 ms-1

Source Time taken for light

to reach us

Distance (m) Working
Moon 1.2 s 3.6 × 108 1.2 × 3 × 108
Sun 8 min 1.44 × 1011 480 × 3 × 108
Next nearest Star 4.3 y 4.07 × 1016 4.3 × 9.46 × 1015
Other side of galaxy 100 000 y 9.46 × 1020 100 000 × 9.46 × 1015
Andromeda galaxy 2 200 000 yr 2.08 × 1022 2 200 000 × 9.46 × 1015
Continuous Spectra

Many light sources produce a continuous spectrum containing all the wavelengths of visible light, e.g. an ordinary light bulb.

Line Spectra.

Some light sources emit only some wavelengths. They produce a line spectrum. Each line corresponds to a particular wavelength.

Each chemical element has its own line spectrum pattern(so it is like a finger print!)

Line spectra can be varied using a spectro-scope in the classroom.

Line spectra are used to tell us about the chemical composition of the stars.

 

 

Dynamics and Space Resources

New Dynamics and Space_2

N5 D&S Problem Booklet

Dynam & Space D&G PS Book

parachutes      parachutes

Projectile questions

Projectile questions

Projectile questions1

mass and weight

mass and weight

work done calculations

Latent Heat questions

Revision Questions

Use the pdf file, printed from a powerpoint presentation to practice work for the D&S topic. Some space has been left so that you can record your answers on the sheets. They are saved 6 slides to a page

Dynamics and Space Revision

Dynamics and Space Revision ANSWERS Don’t peek at the answers until you’ve finished going through the questions and created your own answers.

Resources from other schools

I would like to thank all the schools who have produced notes that are reproduced here. Know that I am really grateful. I have a half finished set of my own notes, but don’t think I can get them suitably done in time. Be assured that at least you’ll have some excellent higher notes next year, and after those scores I am expecting a big Higher class 2017-2018!

Dynamics and space part1

Dynamics and space part2

The above two booklets count as one!

N4 N5 Unit 1 Summary Notes[1]

N4 N5 Unit 1 Summary Notes[1] These are the same set of notes, one is in word, but for those that cannot read that the other is a pdf file, which you ought to be able to read.

D&S Summary Notes

The notes below would be combined into one booklet (the one at the end of this section)

N5 DS Mar 13 Dynamics Teacher notes

N5 DS Mar 13 Forces Pupil notes

N5 DS Mar 13 Forces Teacher notes

N5 DS Mar 13 Space Pupil notes

N5 DS Mar 13 Space Teacher notes

N5 DS Pupil material notes FINAL COPY 13th JUNE

N5 DS Pupil material notes FINAL COPY 13th JUNE

The booklet below is an Intermediate 2 booklet and contains some material for other topics and some material is missing. It might be a good idea to get yourself a copy of this, if possible, especially if you are not a great lover of the heat section!

I2_Mechanics&Heat

Here are some more notes produced for Intermediate 2. There are some good questions here, but it does not cover all of the topic we are about to complete.

3779 Int 2

I will add some cut-outs and single page resources as we go through the course. If you lose yours, you will have to print them off yourself or take a photo!

Other Resources

N5 D&S Problem Booklet

N5 DS Past Paper Booklet

PhysicsCoursePhysicsofFlightLearner_tcm4-752866 PhysicsCoursePhysicsofFlightStaff_tcm4-752868 PhysicsCourseTelescopeLearner_tcm4-756621 PhysicsCourseTelescopeStaff_tcm4-756620

REVISION OF BGE TRANSPORT MATERIALS

Space Junk! We’ve made a bit of a mess of our wonderful world!

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Radiation

Thanks to Miss Horn for the Radiation Notes. Worked Answers to follow.

From Helpmyphysics

Fusion

Fusion is the process when two SMALL NUCLEI join to form a LARGER NUCLEI with the production of ENERGY

Fission

Fission is the process when two large nuclei split to form two smaller nuclei with the production of energy. This can occur spontaneously or due to a collision with a neutron. Often extra neutrons are produced.

Chain Reaction

When neutrons split nuclei by fission and extra neutrons are produced which can split further nuclei. Large quantities of energy are produced.

Reducing exposure to ionising radiation.

There are 3 groups of category to reduce harm caused by radiation:

  1. MONITOR
  2. SHIELD
  3. DISTANCE

Monitor includes things like wearing radiation badges or EPUs, timing how long you are exposed to radiation, checking with radiation counters any contamination on clothes.

Shielding is placing layers of absorbers between you and the source, BEWARE, goggles and a lab coat are great at protecting against alpha but have no effect on gamma. Only thick layers of lead would offer protection against gamma.

Distance. Radiation obeys the inverse square law, as you double the distance from a source the level you are exposed to decreases by ¼ . Using tongs is an effective method of keeping your distance from a source.

When it goes wrong

Chernobyl Nuclear Disaster 1986- Effects and Summary

Chernobyl Surviving Disaster (BBC Drama Documentary)

Chernobyl Questions
  1. What date was the Chernobyl Disaster?
  2. What was the name of the man who hanged himself at the start, who was narrating the story?
  3. Which reactor blew?
  4. What was the cause of the accident?
  5. How many people went to see what had happened?
  6. What happened to the people who saw the hole in the reactor?
  7. What day of the week was the disaster?
  8. What town was evacuated?
  9. How did they drain the water from the reactor?
  10. How did they put out the fire?
  11. What was the reading on the counter when they measured the radiation levels?
  12. Why was this reading misleading and wrong?
  13. What was the real count when it was measured correctly?
  14. What were some of the symptoms of radiation poisoning?
  15. Who was sent to prison for crimes to do with the disaster? (or record how many people went to jail)
  16. Who was president of the USSR when the disaster occurred?
  17. What was the trigger that caused the man to hang himself?
  18. What is the “elephant’s foot?” in the reactor?
  19. Have there been any other nuclear disasters? Can you find out about them and name them?
  20. What other things did you learn about nuclear power stations and radioactivity?
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updated June 2019

Half Life

Half Life

Half Life is the time for the activity to halve.

Time for activity to (decrease by) half
or  time for half the nuclei to decay

 (It is measured in units of time, e.g seconds, minutes, days, years, millions of years!)

Note the SQA do NOT accept: Time for radiation/radioactivity/ count rate to half

half-life-tablehalf-life-formula

From the Yellow Chemcord Book- this is how to answer the questions HALF LIFE QUESTIONS

Chemcord have kindly giving permission to upload these questions here. If you thought they were useful you can buy the National 5 Revision books soon:

Chemcord Sample N5

Chemcord Link

half life Questions A print out for those who would like a copy of the National 5 Chemcord revision questions on half life. Here are the questions written out: HALF LIFE QUESTIONS

  1. What is meant by the half life of a radioactive substance?
  2. The activity of a source drops from 1000 kBq to 125 kBq in 9 days. Calculate the half life of the source.
  3. The activity of a source drops from 4800 kBq to 150 kBq in 10 days. Calculate the half life of the source.
  4. The activity of a source drops from 720 MBq to 45 MBq in 20 years. Calculate the half life of the source.
  5. The activity of a source drops from 4096 kBq to 1 kBq in 2 days. Calculate the half life of the source.
  6. The activity of a source drops from 448 kBq to 3.5 kBq in 17.5 years. Calculate the half life of the source.
  7. A source has an activity of 1800 kBq and a half life of 2 days. What is its activity 10 days later?
  8. A source has an activity of 576 MBq and a half life of 30 years. What is its activity 180 years later?
  9. A source has an activity of 2400 kBq and a half life of 8 s. What is its activity 32 s later?
  10. A source has an activity of 3200 kBq and a half life of 5.3 days. What is its activity 37.1 days later?
  11. A source has an activity of 800 kBq after being stored for 4 days. If the half life is 1 day, what was its initial activity?
  12. A source has an activity of 1800 kBq after being stored for 72 s. If the half life is 24 s, what was its initial activity?
  13. A source has an activity of 40 kBq after being stored for 10 years. If the half life is 2 years, what was its initial activity?
  14. A source has an activity of 30 kBq after being stored for 2 days. If the half life is 8 h, what was its initial activity?
  15. A source has an activity of 40 MBq and a half life of 15 s. How long will it take for its activity to drop to 625 kBq?
  16. A source has an activity of 25 MBq and a half life of 8 days. Approximately how long will it take for its activity to drop to below 1MBq?
  17. A source has an activity of 320 MBq and a half life of 1000 years. Approximately how long will it take for its activity to drop to 500 kBq?
  18. A background count rate of 20 counts per minute is measured in the absence’ of a source. When the source is present the count is 140 counts per minute initially, dropping to 35 counts per minute after 15 days. What is the half life to of the source?
  19. If the background count is 28 counts per minute and the count with a source drops from 932 to 141 counts per minute in 24 h, what is the half life of the source?
  20. If the background count rate is 24 counts per minute and the count rate with a source present drops from 4120 to 25 counts per minute in 2 days, what is the half life of the source?
  21. In an experiment with a radioactive source, the count rate corrected for background radiation was measured and the following results obtained.
Time

in minutes

Corrected

Count Rate

in c.p.m.

0

1

2

3

4

5

100

58

32

18

10

5.6

a) Plot a graph to show these results.

b) Estimate the half life of the source from these results.

22. In an experiment with a source, carried out in an area where there is a high background radiation, the following results were obtained.

Time (s) Count Rate 

(c.p.m.)

0

30

60

90

120

150

180

210

240

270

300

88

72

60

52

44

39

36

34

32

29

30

              

a) Plot a graph to show these results.

b) Estimate the background count rate.

c) Estimate the half life of the source from these results.

ANSWERS

  1. time taken for the activity to decrease by half
  2. 3 days
  3. 2 days
  4. 5 years
  5. 4h
  6. 2.5 years
  7. 56.25kBq
  8. 9 MBq
  9. l50 kBq
  10. 25 kBq
  11. 12.8 MBq
  12. 14.4 MBq
  13. 1.28 MBq
  14. 1920 kBq
  15. 90s
  16. 32 to 40days
  17. 9500 years
  18. 5 days
  19. 8 h
  20. 73.   4h

For Questions 2-6 (to find t ½ when Ao and A known)

Step

  1. Summarise
  2. Starting with the original activity keep halving until you reach the final activity
  3. COUNT THE ARROWS. This is the NUMBER of half lives.
  4. Use the formula    t½= time÷No. of t ½
  5. Don’t forget to write out the time.

 For Questions 7-10 (to find the final activity when t and t ½  are known)  Step

  1. Summarise
  2. Use the formula to find the number of half lives (this will be the number of arrows) No. of t ½ = time÷ t½
  3. Starting with the original activity keep halving until you reach the final activity
  4. COUNT THE ARROWS. This is the NUMBER of half lives.
  5. Don’t forget to write out the units for final activity.

For Questions 11-14 (to find Ao when A, t ½ and time are known)

Steps

  1. Summarise
  2. Use the formula to find the number of half lives (this will be the number of arrows)   No. of t ½ = time÷ t½
  3. DOUBLE the final activity for the number of t ½ eg If you have 4 half lives double the final activity 4 times. NB DO NOT MULTIPLY BY 4
  • The alternative is to MULTIPLY the final activity by 2n (2 to the power n where n is the number of half lives)
  • The number at the end of the arrows is your original activity, don’t forget to add the units.

For Questions 15-17

Step

  1. Summarise
  2. Starting with the original activity keep halving until you reach the final activity
  3. Count the Arrows
  4. Use the formula     time = t½ × No. of t ½

Experiment to Measure Half Life

The activity of a radioactive source decreases time. However the rate of decrease slows with time. Because of this, and because the decay of individual atoms is random and unpredictable, theoretically a radioactive source will never completely lose all of its activity. The time taken for half of the atoms in a radioactive sample to decay is a constant for that source called the half-life of the source. So the half-life of a radioactive source is the time period during which the activity of the source falls to half of its original value. The half-life of some sources is as low as a fraction of a second; for others it is many thousands of years.

Finding the half-life of a radioactive source

Apparatus: Geiger-Muller tube, Scaler counter or ratemeter, Source (eg.sealed protactinium-234 radioactive source and drip tray).

 half-life-exptInstructions:

  • Use the Geiger-Muller tube and scaler counter to measure the back­ground count rate.
  • Record this value.
  • Set up the apparatus shown in the diagram.
  • Measure and record values of count rate and time interval for a suit­able time period.
  • Correct all your measurements for background by taking the background count off all other measured count rates..
  • Plot a graph of COUNT RATE or ACTIVITY against TIME.
  • Find the half life from the graph

half-life-graph

Half life and safety

To measure the half-life of a radioactive source, the level of the background radiation is first measured. Then the count rate with the radioactive source present is measured over a suitable period of time using a suitable detector such as a Geiger-Muller tube connected to a scaler. A graph of the count rate (with the source present), corrected for background radiation, is plotted.A suitable count rate value is chosen, say 80 counts per minute, and the time at which the source had this count rate, t1, is marked as above. In a similar way the time t2 at which the count rate is half the previous value, 40 counts per minute, is found. The half-life of the source is the time period t2 -t1. Any starting value can be chosen, the time period for the count rate to halve in value will always be the same.

EXAMPLE

In six years, the activity of a radioactive isotope drops from 200 kBq to 25kBq. Calculate the half-life of the isotope.

SOLUTION: original activity = 200 kBq 

Activity after 1 half-life = ½ ×200 kBq = 100 kBq

Activity after 2 half-lives = ½ × 100 kBq = 50 kBq

Activity after 3 half-lives = ½ × 50kBq = 25 kBq

 

So 6 years represents 3 half-lives, thus one half-life is 2 years.

Safety with radiation

There are several safety precautions that must be taken when handling radioactive substances.

  • Always handle radioactive substances with forceps. Do not use bare hands.
  • Never point radioactive substances at anyone.
  • Never bring radioactive substances close to your face, particularly your eyes.
  • Wash hands thoroughly after using radioactive substances especially after using open sources or radioactive rock samples.
  • Unauthorised people must not be allowed to handle radioactive substances. In particular, in the United Kingdom, no one under 16 years of age may handle radioactive substances.

In addition there are several safety precautions relating to the storage and monitoring of radioactive substances.

  • Always store radioactive substances in suitable lead-lined containers.
  • As soon as source has been used, return it to its safe storage container, to avoid unnecessary contamination.
  • Keep a record of the use of all radioactive sources.

The equivalent dose received by people can be reduced by three methods:

  • shielding;
  • limiting the time of exposure;
  • increasing the distance from the source.

Stay safe and keep under your annual dose of 2.2 mSv!

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Half life Results- Protactinium-234 and Indium-116

Here are the results from the Protactinium Generator Experiment. Your task is to correct for background (take the background count per second away from the count rate) and then plot a graph of count rate (cps) against time (s). Remember the count rate was taken every 10 s but shows the value of the count rate (for one second)

Background count rate (c.p.m.) 48.0,   46.0,   42.0

Average background count rate (c.p.m.)    45.3

Average background per second (c.p.s.)    work it out!

TimeCount rate
(s)(cps)
080.3
1073.9
2067.3
3060.5
4055.2
5049.6
6045.7
7041.5
8037.4
9034.1
10031.3
11028.5
12025.9
13023.9
14021.7
15019.4
16017.6
17016
18014.9
19013.4
20012.3
21011.2
22010.2
2309.2
2408.4
2507.5
2606.9
2706.4
2805.7
2905.3
3004.7

Pa-234-graph

Indium 116 Half Life

Here are the results for the Indium-116 half life experiment. Warning, do not plot a graph in 15 minute intervals or you will have more difficulty finding the half life. Make the scale ten minute intervals.

You can track the experiment yourself through the link below

Indium-116 files

Background count = 31 c.p.m.

Time Time from startCount rate
(hours)(mins)(c.p.s.)
9:000675
9:1515570
9:3030452
9:4545375
10:0060328
10:1575275
10:3090219
10:45105181
11:00120164
11:15135149
11:30150126
11:45165106
12:0018090

in-116-graph

 

Here are three more examples for you to practice producing a half life graph and for finding the half life of Protactinium

Example 1:

Background Count (cps):    5,   5,   3,  5,   4,   5,   5.

Time (s)Count in 10s
0308
10279
20240
30217
40197
50182
60165
70158
80145
90129
100116
110109
12098
13089
14080
15075
16066
17060
18055
19050
20046
21043
22035

Example 2:

Background Count (cps):     4,       3,      5.

Time (s)Count in 10s
0841
10752
20693
30622
40593
50544
60481
70443
80392
90364
100341
110301
120272
130251
140243
150211
160204
170183
180172

Example 3:

time
(s)
Count
in 10s
corrected
count
in 10s
Corrected
Count
Rate
(cps)
Background
count
(cp10s)
0
5105100.510.055
209590.59.055
358176.57.653
509085.58.555
658681.58.154.5
807368.56.85
957671.57.15
1107974.57.45
1255348.54.85
1405348.54.85
1555853.55.35
1706156.55.65
1856055.55.55
2004338.53.85
2156055.55.55
2304843.54.35
2454540.54.05
2604439.53.95
2754237.53.75
2904742.54.25
3052823.52.35
3203126.52.65
3353631.53.15
3503227.52.75
3652419.51.95

You should now have had plenty of practice at finding the half life graphically, nothing should phase you now.

Signature


Waves Definitions

Here are some definitions to learn for the waves topic. Remember you must be able to spell:

REFLECT, DIFFRACT and REFRACT

Term Definition
Amplitude (A) the distance from the middle of the wave to the top (or the bottom) measured in metres. Maximum displacement from the mean position!
amplitude, (A) maximum disturbance of the particles in a wave. (or distance from middle to top of wave) (m)
Angle of incidence  the angle between an incident ray and the normal (a line perpendicular to the reflecting surface at the point of incidence) (°)
Angle of reflection  the angle between a reflected ray and the normal (°)
Angle of refraction the angle between the light ray in the more optically dense material and the normal. (°)
Critical angle The critical angle is the angle of incidence above which total internal reflection occurs. (°)
Diffraction occurs when wave meet a barrier, the waves bend around an obstacle. Long waves diffract more thank short waves.
Energy and waves Waves transmit energy. The greater the amplitude the more energy is transferred.
Frequency, (f) the number of waves per second. Frequency is measured in hertz (Hz).
Frequency, (f)  number of waves produced or passing a point per second. (Hertz or Hz)
Law of reflection The angle of incidence = the angle of reflection
Longitudinal wave In a longitudinal wave the particles move along the line of the direction of travel of energy.
Normal a line at 90° to the surface at the point of incidence, (from which all angles are measured.)
Period. (T)  Time for one wave to pass a point or time for one wave to be produced. (s)
Principle of reversibility of light The principle of reversibility of light states that a ray of light which travels along any particular path from some point A to another point B travels by the same path when going from B to A.
Reflection when a wave “bounces off” a surface we say it is reflected. (Particles can also reflect)
Refraction when light waves travel from one material to another the waves slow down and there is a reduction in wavelength in the optical thicker material. Unless the waves enter along the normal there is also a change of direction.
Speed, (v) rate of covering a distance. Number of metres travelled per second. (ms-1) The speed of the waves is represented by the formula
Total Internal Reflection When a wave hits a boundary at an angle larger than the critial angle the wave is entirely reflected if the material on the other side of the boundary is less optically dense.
Transverse wave In a transverse wave the particles move at 90 degrees to the direction of the flow of energy.
Wave  a way of transferring energy.
Wave speed the speed at which the wave travels
Wavelength the distance between the same point on successive waves.
Wavelength, (λ)  the distance between two successive points on a wave. (metre or m)
Wavelength, (λ) The wavelength of a wave is the horizontal distance between two adjacent troughs or crests or any two corresponding points on the wave

Wave Resources

Here are a list of current wave resources. I will add more as I go through them. Thanks to other schools if you have kindly supplied material. I really appreciate it as do my students.

wave-radiation-summaryjh-2016

waves-and-radiation-summary-notes1

waves-summary-notes-gairloch1 Some of these notes are for National 4, use with the content statements so you don’t spend too long learning the National 4 work.

vflambda-vdt This starts with a practical model that you can complete in class using the Virtual Physics/ Flash Learning. It then shows how v=fλ is equivalent to v=d/t. Finally some questions will let you practise what you know.

The Gas Laws

The pressure, volume and temperature of a gas all affect one another. This would make the results of an experiment to investigate changes in all three at once complicated to understand. This problem is overcome by making one of them stay constant, whilst the relationship between the other two is investigated.

Boyle’s Law- Volume and Pressure

This Law is about the variation of (a fixed mass of gas) volume with the pressure of a gas at steady temperature. The apparatus shown in the diagrams below may be used to find how the volume of a fixed mass of gas varies with pressure at a constant room temperature.

A syringe can be compressed to increase the pressure which is measured using a pressure sensor. The fixed mass of gas, usually air is trapped in the syringe, and its volume read from the scale.

Alternatively a foot or bicycle pupil is used to increase the pressure which is measured on the Bourdon Gauge. The fixed mass of air is trapped in the capillary tube by a bead of mercury, and its volume measured on the scale.

How Pressure is related to volume for a constant mass and temperature of gas.

Pressure (kPa)100111125143167250
volume of air column(cm 3 )504540353020
Use the results to show a relationship

It is found that when the pressure in increased the volume of the gas decreased so that:

pressure × volume = constant

p × V = k

Boyle’s Law states that: For a fixed mass of gas at constant temperature the pressure is inversely proportional to the volume. i.e. the pressure multiplied by the volume stays constant, provided the temperature does not change.

Kinetic theory of Boyle’s law

The pressure of a gas is caused by the molecules hitting the walls of the container. Reducing the volume results in a shorter distance between the walls and so the number of molecules hitting the walls increases- resulting in increased pressure.

The Pressure Law (Gay Lussac Law)

This law looks at the variation of pressure with temperature at constant volume. The apparatus shown below may be used to find how a fixed mass of gas, at constant volume varies with temperature.

The air is contained in a round bottom flask, which has a constant volume, and the pressure is measured using the pressure sensor attached to the flask by a short tube. It is important to have a short tube so that the temperature in the whole system is equal at any point. The round bottom flask is placed in a water bath which is used to vary the temperature of the water, and hence the air in the flask. Recent results have shown that the thermometer is best placed in the water bath as this gives more accurate results for the temperature of the air in the flask. Placing the thermometer in the flask usually results in a time delay in measuring the temperature of the air inside the flask. The flask should be fully immersed in the water, to ensure all the air in the flask is at the same temperature The temperature must be recorded as Absolute Temperature (in Kelvin) to find a relationship.

The pressure increases proportionally with the absolute temperature (i.e if you double the absolute temperature you will double the pressure provided the mass and volume remain constant). This can be expressed as:

The pressure law states that: For a fixed mass of gas at constant volume the pressure is proportional to the absolute temperature. i.e. the pressure divided by the temperaturee stays constant, provided the volume does not change.

Kinetic theory of Pressure law

If the absolute temperature of a gas increases, the speed of the molecules increases. The force and frequency of the impacts on the walls of the container increases, as this is the cause of pressure,then pressure increases.

How Temperature is related to Pressure for a constant mass and volume of gas.

Temperature ( o C)0205080100
Pressure (kPa)93100110120127
Use this to show a relationship!

Charles’ Law

This is about the variation of volume with temperature at constant pressure. The apparatus shown is used to find how the volume of air varies with temperature provided the pressure remains constant.

The pressure remains constant, since it is equal to the atmospheric pressure plus the small additional pressure due to the weight of the mercury bead on to of the trapped air. This is because the capillary tube is open at one end. The volume of air is measured on the scale and the water bath is used to vary the temperature. The absolute temperature must be used to find a relationship between pressure and volume.

It is found that the volume of the gas increases proportionally with the absolute temperature provided the pressure and mass remain constant. This can be expressed as:

Charles’ Law states that: For a fixed mass of gas at constant pressure the volumee is proportional to the absolute temperature. i.e. the volume divided by the temperature stays constant, provided the pressuree does not change.

 Kinetic theory of Charles’ law

The pressure of a gas is caused by the molecules hitting the walls of the container. If the absolute temperature of the gas increases the speed of the molecules increases. This would result in more forceful and frequent collisions on the walls. However, to maintain the pressure then there must be no increase in the frequency and magnitude of the collisions, so the volume must increase.

How Temperature is related to volume for a constant mass and pressure of gas.

Temperature ( o C)020406080100
Length of air Column(cm)2021.522.924.425.927.3
Proportional to volume
Use these figures to show a relationship!

 The General Gas Law

The three separate gas laws can be summarised by one equation, known as the General Gas Equation:

This is often written as:

Where p1, V1 and T1 refer to one set of conditions of pressure volume and temperature, and p2, V2 and T2 to another set of conditions for the same mass of the same gas.

An individual gas law can be found from this equation by covering up the variable which is kept constant (or cancelling out the variable as it remains constant).

gas law results docx

gas law result pdf

Complete the three graphs above and for two of them try to work out the equation for the straight line, i.e. what is y = mx + c

Pascal

The unit of pressure is the Pascal. I Pa is 1 Nm-2. You must remember you will not measure zero pressure as we have an atmosphere. I atmosphere is the pressure exerted due to our atmosphere and is approximately equal to 1 x105 Pa. This is equivalent to a weight of 105 N acting on a square of area 1m2. At ground level this is approximately the mass of 104 kg on a square metre which equates to about 10 Fiat 500 in 1m2.

Questions

  1. A mass of gas at a pressure of 20kPa has a volume of 3m3. What will be the volume if the pressure is doubled but the temperature remains constant?
  2. The volume of mass of a gas is reduced from 5m3 to 2m3. If the pressure was initially 40 Pa, what will be the new pressure if the temperature remains constant?
  3. The pressure of a fixed volume of gas at 300 K is increased from 5 Pa to 10 Pa, what will the new temperature be?
  4. If pressure of a fixed volume of gas at 200 K is 50 Pa. What would be the pressure if the temperature is increased to 300 K?
  5. The temperature of 6 m3 of gas is increased from 300 K to 400 K. What will be the new volume of the gas if the pressure remains constant?
  6. The volume of a gas is increased from 10 m3 to 20 m3 at constant pressure. Calculate the new temperature if the initial temperature was 300 K.
  7. A mass of gas has a volume of 5 m3, a pressure of 20 Pa and a temperature of 300 K. What will be the new pressure if the volume is changed to 4m3 and the temperature to 400 K?

Answers

  1. 1.5 m3,
  2. 100 Pa
  3. 600 K
  4. 75 Pa
  5. 8 m3
  6. 600 K
  7. 33 Pa
Signature
May 2019

 


Voltage

gills-book

Many teachers think that voltage is too difficult a concept for S1 students to understand. By the time students get to AH we expect them to be fully knowledgeable about voltage, but we don’t clearly explain it to them as we go along. I am as guilty as the next person of doing this so… . My new mission is to teach voltage as best and as fully as I can to S1 and build on the concept each year so that by AH they will feel confident about this work.

Having met Gill Arbuthnott at the Edinburgh International Book Festival (see post in Blog) I was really impressed with the way she tries to explain difficult concepts early on. She has given me permission to reproduce her page 16 on The Volt here.

The Volt

This was named after Alessandro Volta It is a unit of measurement in electricity. It tells us how much energy an electric charge has. You sometimes hear people saying things like, “The number of volts running through the circuit is…”. This doesn’t actually make sense! It’s like saying, “The height running through the mountain is 1000 metres.” Heights don’t run, and neither do volts. There is no Usain Volt!

What is a volt?

So what is a volt? Imagine you are in a building with stairs and a lift. You carry a tennis ball up one floor in the lift, and let it roll back to ground level down the stairs. A battery is like the lift – it’s a way of giving energy to something. In the building this is the ball – in electrical terms it’s an electron.

The ball rolling down the stairs is losing energy. In our circuit the equivalent is the electrons losing their energy to power a bulb. The voltage is equivalent to the height you take the ball up in the lift – more height is equivalent to greater voltage. And the distance the ball goes up in the lift must be the same as the distance it comes down by the stairs.

There are plenty of pictures in the book, but I didn’t think it was as easy to reproduce them. The book is full of more really interesting stuff, and even material about coins that Mr Chemistry opposite Mrs Physics didn’t know about (but then he’s far too young!)

http://www.bloomsbury.com/uk/a-beginners-guide-to-electricity-and-magnetism-9781472915740/

Definition: Potential difference is the amount of work done to move an electric charge from one point to another.

or

Definition: The definition of voltage is the electromotive force or the electrical potential difference between two points in a circuit expressed in volts.

Voltage is a scalar quantity. The SI unit of voltage is the volt, such that 1 volt = 1 joule/coulomb.

The easiest way to understand voltage is to use a water analogy. Using a hose as an example, think of voltage as the amount of pressure forcing water through a garden hose. The higher the pressure in the pipe the more water is forced through the pipe each second. The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time Q=It) through a conducting or semiconducting medium for a given resistance to the flow.

One volt will drive one coulomb (6.24 × 10 18 ) charge carriers, electrons, through a resistance of one ohm in one second.

Voltage can be direct or alternating. A direct voltage maintains the same polarity at all times. So charges always flow in one direction. In an alternating voltage, the polarity reverses direction periodically. The number of complete cycles per second is the frequency, which is measured in hertz (one cycle per second). An example of direct voltage is the potential difference between the terminals of a cell. Alternating voltage exists between the mains positive and negative.

 

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Update Electricity and Energy Resources

fuses-and-earthing-2016 docx

fuses-and-earthing-2016 pdf

ring-main   ring-main

Fuses & Earth Polly demo

wiring

From the lessons see the notes on voltage divider circuits

voltage divider circuits pdf

voltage divider Q        voltage divider Q pdf

potential-dividers       potential-dividers pdf

Uploading from school is 100 × quicker than home or the mobile!

IPO devices

Additional Capacitor Notes

input output tutorial

electronics

LED

8c. Flashcards VIR

series and parallel model

continuity tester

CIRCUITS PROBLEMS

Electrons and Charge

Setting up V and A

V I R expt

resistance

Resistor Network

VOLTAGE DIVIDER FORMULAE

motor applets

Motors and Electromagnets

motor notes2

Transistors

VOLTAGE divider NO NPN

VOLTAGE divider circuits

POTENTIAL DIVIDERS2

VOLTAGE divider circuits

31b. PIV

QIt

transformer Q colour

Generating Electricity

Current through a wire

N5 Energy and Electricity National 5 Physics E&E Revision (INT2)

NAT5 STUDY GUIDE Electricity and Energy textbook updated

N45 Electricity 1 20Q

national 5 Electricity june

Nat45 E&E videoclips & info

Ring main

Some revision stuff