Year 9 Wave Booklet Answers

Page 4 Questions

1. All waves are produced by an oscillating (vibrating) object.2. Another word for oscillating is vibrating.3. Electromagnetic waves are caused when the vibrating object is a charged particle. A

vibrating charge creates a changing magnetic field, which in turn creates a changing electric field, which in turn creates another changing magnetic field and this process repeats until the wave hits an object.

4. Protons and electrons are charged particles.

Page 5 Questions

1. Point f2. Point g3. Point h4. Point i5. The distance between two equivalent points on adjacent waves is the wavelength.6. Lamda ( l )7. Metres (m)

Page 7 Questions

1. Peaks2. Troughs3. Wavelength4. The number of complete wave cycles per second.5. Frequency symbol = f6. Frequency unit = Hertz, Hz7. 15 complete wave cycles in one second8. 600 complete wave cycles in one second9. Frequency and time must always multiply together to equal 1.10. 5Hz11. 0.04Hz12. 2s13. 0.025s14. 6Hz15. 5Hz16. The frequency will increase as the number of vibrations from the motor will increase.

Page 8 Questions

1. Velocity = frequency x wavelength2. Velocity = 38 x 0.18 =6.84 m/s3. Velocity = 460 x 2.6 = 1196 m/s4. Velocity = 9.4 x 3.2 = 30.08 m/s5. 3.8 = frequency x 0.7, frequency = 5.43 Hz6. 13 = frequency x 4.4, frequency = 2.95 Hz7. 670 = frequency x 0.05, frequency = 13400 Hz8. 550 = 11 x wavelength, wavelength = 50m9. 78 = 20 x wavelength, wavelength = 3.9m10. 48 = 6 x wavelength, wavelength = 8m11. 2.5 = frequency x 5, frequency = 0.5Hz12. 2 seconds13. Speed = 24 x 2, speed = 48 m/s14. 0.042 seconds15. 14 = (1/20) 0.05 x wavelength, wavelength = 280m16. Speed = 3.1 x 104 x 6.23 x 10-3 = 193.13 m/s17. 2.4 x 107 = 5.5 x 102 x wavelength, wavelength = 43636 m = 4.4 x 104 m18. Velocity = 8.3 x 10-6 x 9.1 x 105 = 7.553 = 7.6 x 100 m/s19. 4.6 x 104 = frequency x 2.9 x 105 = 0.16 Hz = 1.6 x 10-1 Hz20. Frequency = 5/2 = 2.5 Hz, time period = 0.4 s21. 6.7 x 104 = 5.0 x 106 x wavelength, wavelength = 0.0128m = 1.28 x 10-2 m22. 10,000 MHz = 10,000,000,000 Hz x 0.03 = Speed = 300,000,000 m/s23. 3 x 108 = frequency x 0.60, frequency = 500,000,000 Hz24. 450,000kHz = 450,000,000 Hz so 300,000,000 = 450,000,000 x wavelength, wavelength =

0.67m25. 6.5 = 2.5 x wavelength, wavelength = 2.6m

Page 14 Questions

1. Refraction occurs when light travels from one medium (material) to another and changes direction.

2. Two examples of using refraction is lenses in the eye, glasses, telescopes and microscopes.3. Light can travel through air, water, glass, diamond, plastic, vacuums.4. Two media more dense than air are glass and diamond and water.

5. See diagram below

6. If the change of medium goes from less dense to more dense, then the refracted ray bends

towards the normal, if the medium goes from more dense to less dense the ray bends away from the normal.

7. See diagram below

8. See diagram below

9. See diagram below

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12. See diagram below

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17. See diagram below

Page 21 Questions

1. Waves transfer energy.2. Particles in a wave oscillate (vibrate) around a fixed point and transfer the energy.3. An oscillation is a vibration.4. In a longitudinal wave, the oscillations are parallel to the direction of energy transfer.5. Diagram of longitudinal wave drawn into your notes.6. Sound and ultrasound are longitudinal waves7. In a transverse wave, the oscillations are perpendicular (at right angles) to the direction

of energy transfer.8. Diagram of a transverse wave drawn into your notes.9. Light and water waves are both transverse.10. Longitudinal waves have oscillations that are parallel to the direction of wave travel

whereas transverse waves have oscillations at right angles to the direction of energy travel.

11. Yes waves transfer energy.12. No particles of matter are not transferred by waves, the particles move but always end

up in their original position.13. Experiment could be the one with the helium balloon next to loudspeaker shown in the

booklet on page 21.14. If a sound wave is moving from left to right through air, then particles of air will be

displaced both rightward and leftward as the energy of the sound wave passes through it. The motion of the particles is parallel (and anti-parallel) to the direction of the energy transport. This is what characterizes sound waves in air as longitudinal waves.

15. Experiment could be the one with the object floating on water on page 21.16. A boat at rest on the ocean moves up and down as water waves pass beneath it.

The waves appear to be moving toward the shore. But the water particles that make up the wave are actually moving in a vertical direction. The boat itself does not move toward the shore as the wave motion is transverse.

17. This is a longitudinal wave as it contains compressions and rarefactions.

18. 90o as water is an example of a transverse wave19. 0o or 180o as sound is an example of a longitudinal wave20. A compression is an area of high density in a longitudinal wave, where the particles are

squashed together.21. A rarefaction is an area of low density in a longitudinal wave, where the particles are

spread out.