Waves Questions

Question 0

State the proportionality of intensity to amplitude.

Answer 0

Intensity = Amplitude^2

Question 1

With reasons, state two apparatus’ used to measure the frequency of sound waves.

Answer 1

Microphone — transfer mechanical motion to electrical signal.

Oscilloscope — to display oscillation for measurement of period.

Question 2

How would you find out the amplitude of air motion on a graph?

Answer 2

Find the maximum amplitude (peak) of a wave on the graph.

Question 3

How would you find the frequency of a sound wave on a graph? State the formula.

Answer 3

Frequency = 1/t (1 full oscillation/time taken).

Question 4

Define the term “Node” on a stationary wave.

Answer 4

A node occurs where the amplitude/displacement is (always) zero.

Question 5

Antinode

Answer 5

Occurs where amplitude takes maximum possible value.

Question 6

Explain with reference to a progressive wave how a stationary wave is formed.

Answer 6

1. The wave travels to the end and is reflected.
2. The reflected wave interferes with the incident wave.
3. Always constructively/destructively at certain points to make anti/nodes.

Question 7

Describe an experiment to demonstrate the polarisation of microwaves in the laboratory.

Answer 7

1. Place transmitter and receiver facing each other.
2. Rotate either transmitter or receiver through 90o about axis joining aerials
   waves are transverse / use two polarising filters and rotate from parallel to crossed.
3. Observe signal fall to minimum from initial high value on meter monitoring output of receiver.

Question 8

State the four main wave phenomena that apply to both EM waves and sound waves.

Answer 8

Diffraction / Refraction / Superposition / Interference.

Question 9

Explain why electromagnetic waves can be polarised but sound waves cannot.

Answer 9

Only transverse waves can be polarised.