brodidit for students
Home / Practice / NET / Physics / Waves and sound
Waves and sound
5 NET Physics questions with answers and explanations.
Printable worksheet with answer key
-
A string has a tension of 100 N and a mass per unit length of 0.01 kg/m. What is the speed of a wave on it?
- 1 100 m/s
- 2 1000 m/s
- 3 10 m/s
- 4 50 m/s
Show answer
Correct answer: 100 m/s
v = sqrt(T / mu) = sqrt(100 / 0.01) = sqrt(10000) = 100 m/s.
-
What is the fundamental frequency of an open pipe 1 m long? (Speed of sound 340 m/s)
- 1 680 Hz
- 2 85 Hz
- 3 340 Hz
- 4 170 Hz
-
When the intensity of a sound is doubled, the sound level rises by about:
- 1 1 dB
- 2 6 dB
- 3 3 dB
- 4 10 dB
Show answer
Correct answer: 3 dB
The level is 10 log(I₂ / I₁) = 10 log 2, which is about 3 dB.
-
An observer moves towards a stationary source of sound. The frequency heard is:
- 1 Zero
- 2 Higher than the source frequency
- 3 Lower than the source frequency
- 4 The same as the source frequency
Show answer
Correct answer: Higher than the source frequency
The observer meets the wave fronts more often, so the apparent frequency is higher.
-
In a standing wave, the distance between two adjacent nodes is:
- 1 A quarter of a wavelength
- 2 Half a wavelength
- 3 One wavelength
- 4 Two wavelengths
Show answer
Correct answer: Half a wavelength
Nodes are separated by half a wavelength, and antinodes lie midway between them.