Section 3-Waves P2

Question 1

What type of waves are sound waves and what are they made up of?

Answer 1

• Longitudinal Waves

- vibrations passed through a series of compressions and rarefactions

Question 2

What’s the standard human hearing range?

Answer 2

20 - 20000Hz

Question 3

How do different mediums affect sound waves?

Answer 3

Because sound waves are caused by vibrating particles

• the denser the medium the faster the sound travels
• sound can’t travel through a vacuum

Question 4

How can sound be reflected or absorbed?

Answer 4

• reflected by hard flat surfaces

- absorbed by absorbing surfaces(e.g. carpets)

Question 5

What happens when sound waves enter a different medium?

Answer 5

Sound waves refract when they enter a different medium

-the denser the medium the faster the wave will travel

Question 6

What can a sound wave receiver do?

Answer 6

It can pick up sound waves travelling through the air

Question 7

What does an oscilloscope do?

Answer 7

An oscilloscope is a device which can display the microphone signal as a trace on a screen.

• the appearance of the wave tells you its amplitude and frequency
• you can even take detailed measurements to calculate the frequency

Question 8

What is the link between the amplitude of a wave and the loudness?

Answer 8

-the greater the amplitude(height from rest) of a wave, the more energy it carries which means the sound will be louder

Question 9

What’s the link between the frequency of a wave and the pitch of a sound?

Answer 9

-The higher the frequency(number of complete waves per second), the higher the pitch

Question 10

Describe a practical which allows you to find the period of a wave on an oscilloscope to get its frequency:

Answer 10

• horizontal axis on oscilloscope is time
• time between each division on the scale can be adjusted to get a clear, readable trace
• adjust the time setting until the display shows at least one complete wave
• read off the period and work out the frequency from that

Question 11

Describe a practical of how you can use an oscilloscope to measure the speed of sound:

Answer 11

• attach a signal generator to a speaker to generate sounds with a specific frequency
• use 2 microphones and an oscilloscope to find the wavelength of the sound generated
  1) the detected waves at each microphone can be seen as a separated wave on the oscilloscope
  2) slowly move one microphone further away so the two waves are aligned on the display but are one wavelength apart
  3) measure the distance between the microphones to find the wavelength
  4) use the formula v = fλ to find the velocity, the frequency is what you set the signal generator to
• speed of sound in air is 340m/s