5.1.3 - Sound Properties and Use

Question 1

What is refraction?

Answer 1

When a wave travels from one medium to another, its velocity can change, as well as its medium.

Question 2

When entering a more dense medium, does the wave speed up or slow down?

Answer 2

Slows down.

Question 3

When entering a more dense medium, does the wave bend towards or away from the normal?

Answer 3

Towards.

Question 4

Which is more dense, cold air or hot air?

Answer 4

Cold air.

Question 5

When entering a less dense medium, does the wave speed up or slow down?

Answer 5

Speed up.

Question 6

When entering a less dense medium, does the wave bend towards or away from the normal?

Answer 6

Away from.

Question 7

When does a sound become an ultrasound?

Answer 7

When it has a frequency greater than 20,000Hz.

Question 8

Can humans hear ultrasound?

Answer 8

No, but some animals can.

Question 9

What does speed spread out around?

Answer 9

A source.

Question 10

What can ultrasounds do that sound waves cannot?

Answer 10

Be focused into a small beam.

Question 11

How can ultrasound be used to produce an image of a baby?

What else can this method be used for?

Answer 11

1. Transmitter beams ultrasound waves into the mother.
2. Waves refracts from different boundaries.
3. Machine calculates the distances using time and velocity.
4. Uses this distance to produce an image.

To find the depth of water.

Question 12

What are the two machines that can be used to find the depth of water?

Answer 12

1. Echo-sounders.

2. Sonar.

Question 13

What are the three things that waves can do when they hit a boundary?

Answer 13

• Reflect.
• Transmit (and possible refract).
• Absorb.