xavier catholic college physics the world communicates
XAVIER CATHOLIC COLLEGE
PHYSICS
THE WORLD COMMUNICATES
Homework Answers Homework 1: Energy Transfers List of Energies Sound energy Electric energy Radio waves
Flowchart
Sound waves (Sound Energy = Kinetic Energy of particles of medium e.g. air, then microphone membrane) —> Electric signal (Electrical Energy of electrons in mobile phone circuitry) —> Radio
waves (Electromagnetic Energy i.e Electric & magnetic fields oscillating as two transverse waves at right angles to each other) —> Electric signal (Electrical Energy of electrons in aerial of Base Station) —> Electrical impulses (Electrical Energy of electrons in cable network) —> Three options —> 1 Light pulses (Light Energy in optical fibre network) —> 2 Electrical impulse (Electrical Energy of electrons in copper wire network)
—> 3 Electrical impulse (Electrical Energy of electrons in switching and base station circuitry) —> Radio waves (Electromagnetic Energy – see above) The reception side of things is basically a reverse of the above with various permutations depending on the phones used and the age of the phone cable network.
H-Answers to H1-13.doc
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Homework 2: Waves Transfer Energy •
• •
•
•
All waves are the result of a vibration e.g. o Water waves from a pebble dropped in a pond o Sound waves from human vocal cords vibrating o Radio waves from electrons oscillating in an aerial Waves transfer energy away from the source of the vibration Waves can be one, two or three dimensional e.g. o Longitudinal or transverse waves in a slinky spring = one dimensional o Water waves from a pebble dropped in some still water = two dimensional o Sound & light waves travel as a spherical wavefront = three dimensional Waves transfer energy without transferring matter e.g. o Surfer bobbing up and down in a swell o Free end of rope jerks at a post o Slinky spring knocking over an object through its sideways motion Waves are a disturbance travelling through a medium and are the most important means of transferring energy through the universe
Homework 3: The Wave Equation 1. MW
MW
SW
SW
VHF
VHF
f
695
711
5975
5980
93.3 MHz
94.1 MHz
λ (m)
431.65
421.9
50.21
50.17
3.215
3.188
2. a. 431.65 m, MW 695 kHz, b. no, c. 215.83 m, no, d. 107.91, yes 3. 14.7 cm, 14.0 cm.
Homework 4: Wave Graphs 1. a. b. c. d. e.
Waves s-1 or cycles s-1 0.4 m 4.0 ms-1 0.1 s same.
2. a. i. 1.0 m ii. 5 x 10-5 m iii. 330 Hz b. A transverse wave pattern on the screen is representing a longitudinal wave i.e. sound. 3. a. i. B and D ii. A H-Answers to H1-13.doc
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iii. Anywhere between A and B or A and D. b. Yes. No, direction is different.
Homework 5: Longitudinal Waves 1. a. b. c. d. e.
8 x 10-4 2 x 10-3 500 Hz 7 x 10-4 4 x 10-3
cm s cm ms-1.
Homework 6: Speed of Sound 1. a. 198.0 m b. Speed of sound is constant c. i. No ii. No. Speed varies with the properties of the air. 2. a. 37.5 m b. 18.75 m 3. Absorb, rather than reflect, sound waves. 4. Spring back faster. 5. John by 2.83 s.
Homework 7: Superposition of Waves 1. a. Straight line b. Superimposed c. i. arrow up ii. arrow down — same length d. Equal in size, opposite in direction e. 0 f. Yes g. Destructive 2. a. Produce a large crest b. Constructive c. +2x m
Homework 8: Electromagnetic Spectrum 1. 2. 3. 4. 5.
3.0 x 10 -5 m x 100 UVA, UVB > 300 nm 117.3 MJ 422.7 W
H-Answers to H1-13.doc
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Homework 9: Limitations of Electromagnetic Radiation for Communication Read pg. 37 – 40 of your text to address this dot point. Most of the attention here will be on the radio waves i.e. AM/FM, microwave and light wave modulation for communication.
Homework 10: Law of Reflection 1.
2.
H-Answers to H1-13.doc
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3.
Homework 11: Reflection as used in Communication Read through pg. 48 – 49 and 53 – 55 to help you with the relevant dot points.
Homework 12: Refraction 1.
H-Answers to H1-13.doc
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Homework 13: Snell’s Law 1. a) a. b. c. d. e. b) a. b. c. d. e.
37˚ 30˚ 22˚ 22˚ 37˚ incidence refraction refraction incidence refraction
2. a. blue — the angle of refraction is smaller indicating that it has slowed down less than the red light. b. Red light = 1.677 Blue light = 1.468 c. velocity red : velocity blue = 0.881 : 1 3. a. 48˚ 36’ b. 1.5
H-Answers to H1-13.doc
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PHYSICS
THE WORLD COMMUNICATES
Homework Answers Homework 1: Energy Transfers List of Energies Sound energy Electric energy Radio waves
Flowchart
Sound waves (Sound Energy = Kinetic Energy of particles of medium e.g. air, then microphone membrane) —> Electric signal (Electrical Energy of electrons in mobile phone circuitry) —> Radio
waves (Electromagnetic Energy i.e Electric & magnetic fields oscillating as two transverse waves at right angles to each other) —> Electric signal (Electrical Energy of electrons in aerial of Base Station) —> Electrical impulses (Electrical Energy of electrons in cable network) —> Three options —> 1 Light pulses (Light Energy in optical fibre network) —> 2 Electrical impulse (Electrical Energy of electrons in copper wire network)
—> 3 Electrical impulse (Electrical Energy of electrons in switching and base station circuitry) —> Radio waves (Electromagnetic Energy – see above) The reception side of things is basically a reverse of the above with various permutations depending on the phones used and the age of the phone cable network.
H-Answers to H1-13.doc
Page 1 of 6
Homework 2: Waves Transfer Energy •
• •
•
•
All waves are the result of a vibration e.g. o Water waves from a pebble dropped in a pond o Sound waves from human vocal cords vibrating o Radio waves from electrons oscillating in an aerial Waves transfer energy away from the source of the vibration Waves can be one, two or three dimensional e.g. o Longitudinal or transverse waves in a slinky spring = one dimensional o Water waves from a pebble dropped in some still water = two dimensional o Sound & light waves travel as a spherical wavefront = three dimensional Waves transfer energy without transferring matter e.g. o Surfer bobbing up and down in a swell o Free end of rope jerks at a post o Slinky spring knocking over an object through its sideways motion Waves are a disturbance travelling through a medium and are the most important means of transferring energy through the universe
Homework 3: The Wave Equation 1. MW
MW
SW
SW
VHF
VHF
f
695
711
5975
5980
93.3 MHz
94.1 MHz
λ (m)
431.65
421.9
50.21
50.17
3.215
3.188
2. a. 431.65 m, MW 695 kHz, b. no, c. 215.83 m, no, d. 107.91, yes 3. 14.7 cm, 14.0 cm.
Homework 4: Wave Graphs 1. a. b. c. d. e.
Waves s-1 or cycles s-1 0.4 m 4.0 ms-1 0.1 s same.
2. a. i. 1.0 m ii. 5 x 10-5 m iii. 330 Hz b. A transverse wave pattern on the screen is representing a longitudinal wave i.e. sound. 3. a. i. B and D ii. A H-Answers to H1-13.doc
Page 2 of 6
iii. Anywhere between A and B or A and D. b. Yes. No, direction is different.
Homework 5: Longitudinal Waves 1. a. b. c. d. e.
8 x 10-4 2 x 10-3 500 Hz 7 x 10-4 4 x 10-3
cm s cm ms-1.
Homework 6: Speed of Sound 1. a. 198.0 m b. Speed of sound is constant c. i. No ii. No. Speed varies with the properties of the air. 2. a. 37.5 m b. 18.75 m 3. Absorb, rather than reflect, sound waves. 4. Spring back faster. 5. John by 2.83 s.
Homework 7: Superposition of Waves 1. a. Straight line b. Superimposed c. i. arrow up ii. arrow down — same length d. Equal in size, opposite in direction e. 0 f. Yes g. Destructive 2. a. Produce a large crest b. Constructive c. +2x m
Homework 8: Electromagnetic Spectrum 1. 2. 3. 4. 5.
3.0 x 10 -5 m x 100 UVA, UVB > 300 nm 117.3 MJ 422.7 W
H-Answers to H1-13.doc
Page 3 of 6
Homework 9: Limitations of Electromagnetic Radiation for Communication Read pg. 37 – 40 of your text to address this dot point. Most of the attention here will be on the radio waves i.e. AM/FM, microwave and light wave modulation for communication.
Homework 10: Law of Reflection 1.
2.
H-Answers to H1-13.doc
Page 4 of 6
3.
Homework 11: Reflection as used in Communication Read through pg. 48 – 49 and 53 – 55 to help you with the relevant dot points.
Homework 12: Refraction 1.
H-Answers to H1-13.doc
Page 5 of 6
Homework 13: Snell’s Law 1. a) a. b. c. d. e. b) a. b. c. d. e.
37˚ 30˚ 22˚ 22˚ 37˚ incidence refraction refraction incidence refraction
2. a. blue — the angle of refraction is smaller indicating that it has slowed down less than the red light. b. Red light = 1.677 Blue light = 1.468 c. velocity red : velocity blue = 0.881 : 1 3. a. 48˚ 36’ b. 1.5
H-Answers to H1-13.doc
Page 6 of 6
