امواج اور آواز

Written by Dr. Hamza Farooq (Physics)

نیٹ · طبیعیات · 5 سوالات

نام: ____________________ تاریخ: ____________

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?
- A 100 m/s
- B 1000 m/s
- C 10 m/s
- D 50 m/s
What is the fundamental frequency of an open pipe 1 m long? (Speed of sound 340 m/s)
- A 680 Hz
- B 85 Hz
- C 340 Hz
- D 170 Hz
When the intensity of a sound is doubled, the sound level rises by about:
- A 1 dB
- B 6 dB
- C 3 dB
- D 10 dB
An observer moves towards a stationary source of sound. The frequency heard is:
- A Zero
- B Higher than the source frequency
- C Lower than the source frequency
- D The same as the source frequency
In a standing wave, the distance between two adjacent nodes is:
- A A quarter of a wavelength
- B Half a wavelength
- C One wavelength
- D Two wavelengths

جوابی کلید

1. A, 2. D, 3. C, 4. B, 5. B

v = sqrt(T / mu) = sqrt(100 / 0.01) = sqrt(10000) = 100 m/s.
For an open pipe f = v / 2L = 340 / 2 = 170 Hz.
The level is 10 log(I₂ / I₁) = 10 log 2, which is about 3 dB.
The observer meets the wave fronts more often, so the apparent frequency is higher.
Nodes are separated by half a wavelength, and antinodes lie midway between them.