### Doppler 1 Background

Active

(Click the question to get the answer.)

1. What is meant by the term "frequency" of a sound wave?
This is the number of vibrations that occur per second.
Audio 1

2. What is the symbol and unit for frequency??
The symbol for frequency is f.
The unit for frequency is hertz or Hz.
Audio 2

3. What is meant by the wavelength of a wave?
This is the distance between two consecutive points in phase.
(It is the actual length of the wave before it repeats itself.)
Audio 3

4. What is the symbol and unit for wavelength?
The symbol for wavelength is the Greek letter λ.
The unit for wavelength is m (meters).
Audio 4

5. Write down the simple wave equation.
v = fλ
Audio 5

6. The wavelength of a sound wave is 0,85m, and its frequency is 400Hz.
Calculate its speed v.
v = fλ
v = (400)(0,85)
v = 340m.s-1
Audio 6

7. Are sound waves "longitudinal" or "transverse"?
Longitudinal
The direction of vibrations and the direction of the movement are in the same direction.
Audio 7

8. What is meant by the period T of a wave, and how is it calculated?
This is the duration of a single wave, measured in s (seconds)
This is the time for which a single wave existed.

T = 1/f

Audio 8

9. The frequency of a wave is 400Hz. Calculate its period T?
T = 1/f
T = 1/400
T = 0,0025 s
T = 2,5 x 10-3 s
Audio 9

10. The speed of a sound wave is 340m.s-1, the period is 2 x 10-3 s. Calculate its wavelength λ.
Calculate the frequency.
T = 1/f
2 x 10-3 = 1/f
f = 500Hz

Since
v = fλ
340 = 500λ
λ = 0,68 m

Audio 10