3.2 Wave Speed

Question 1

What is the equation for wave speed?

Answer 1

Wave speed = frequency x wavelength

Question 2

What speed do electromagnetic waves travel?

Answer 2

All electromagnetic waves travel at a speed of c (3 x 10^8 m/s) in a vaccum

Question 3

What is a way to measure the speed of sound in a lab?

Answer 3

• Use two microphones in a straight line a distance d apart
• The microphones should have separate inputs so the signals from each can be recorded separately
• Use the signal generator to produce a sound from the loud speaker and use the computer to record the time between the first and second microphone picking up the sound
• Do this by measuring the time delay between the first peak of the signal received by each microphone on a graph of voltage against time.

Question 4

How would you do an experiment to measure the speed of wave travelling through water?

Answer 4

• set up a ripple tank
• record the depth of water in the tank using a ruler
• use the ripple tank dipper to create vibrations with a regular frequency in the tank
• dim the lights in the room and turn on the strobe light above the tank
• increase the frequency of the strobe light from zero until the waves appear to be standing still. This is when the frequency of the light is equal to the frequency of the water waves
• use an attached ruler to measure the distance between two adjacent peaks (the wavelength)
• repeat for a range of depths