Physic Homework 1 Class 8

 Sound is a form of energy that spreads out through space.

Part 1

1. Sound waves with frequencies below 20 hertz are called …….

Sound waves with frequencies above
20,000 hertz are called …….

Humans can …….. sound waves. Dogs, however, can hear frequencies of

2. What is the source of all sound?

Part.2

1. The sound waves that humans cannot hear are those with frequencies
1. from 20 to 20,000 Hz.
2. below 20 Hz.
3. above 20,000 Hz.
4. both B and C
2. Sound travels in air by a series of
1. compressions.
2. rarefactions.
3. both compressions and rarefactions.
4. pitches.

3. Sound travels faster in 
1. a vacuum compared to liquids.
2. gases compared to liquids.
3. gases compared to solids.
4. solids compared to gases.

4. The speed of sound varies with
1. amplitude.
2. frequency.
3. temperature.
4. pitch.

5. The loudness of a sound is most closely related to its
1. frequency.
2. period.
3. wavelength.
4. intensity.

6. When you tap various objects they produce characteristic sounds that are related to
1. wavelength.
2. amplitude.
3. period.
4. natural frequency.

7. When the surface of a guitar is made to vibrate we say it undergoes   
1. forced vibration.
2. resonance.
3. refraction.
4. amplitude reduction.
8. When an object is set into vibration by a wave having a frequency that matches the natural frequency of the object, what occurs is 
1. forced vibration.
2. resonance.
3. refraction.
4. amplitude reduction.

9. Noise-canceling devices such as jackhammer earphones make use of sound
1. destruction.
2. interference.
3. resonance.
4. amplification.
10. The phenomenon of beats is the result of sound
1. destruction.
2. interference.
3. resonance.
4. amplification.