Waves

A pipe open at both ends has a fundamental frequency f in air. The pipe is now dipped vertically in a water drum to half of its length. The fundamental frequency of the air column is now equal to:

1. 3f2
2. 2f
3. f2
4. f

The displacement of a travelling wave y = C 2 (at - x) where t is time, x is distance and is the wavelength, all in S.I. units. Then the frequency of the wave is

1. 2 a
2. 2 a
3. a
4. a

The ratio of frequencies of fundamental harmonic produced by an open pipe to that of closed pipe having the same length is

1. 2:1
2. 1:3
3. 3:1
4. 1:2

If the initial tension on a stretched string is doubled, then the ratio of the initial and final speeds of a transverse wave along the string is

1. 1 : 1
2. 2 : 1
3. 1 : 2
4. 1 : 2

An organ pipe filled with a gas at 27 resonates at 400 Hz in its fundamental mode. If it is filled with the same gas at 90 , the resonance frequency at the same mode will be

1. 512 Hz
2. 420 Hz
3. 440 Hz
4. 484 Hz

In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases. If the frequency of A is 530 Hz, the original frequency of B will be :

1. 524 Hz
2. 536 Hz
3. 537 Hz
4. 523 Hz

A tuning fork is used to produce resonance in a glass tube. The length of the air column in this tube can be adjusted by a variable piston. At room temperature of 27°C two successive resonances are produced at 20 cm and 73 cm of column length. If the frequency of the tuning fork is 320 Hz, the velocity of sound in air at 27°C is

1. 330 m s-1
2. 339 m s-1
3. 350 m s-1
4. 300 m s-1

The fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. If the length of the closed organ pipe is 20 cm, the length of the open organ pipe is

1. 13.2 cm
2. 8 cm
3. 12.5 cm
4. 16 cm

The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system ?

1. 20 Hz
2. 30 Hz
3. 40 Hz
4. 10 Hz

Two cars moving in opposite directions approach each other with speed of 22 m s-1 and 16.5 m s-1 respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is (velocity of sound is 340 m s-1)

1. 361 Hz
2. 411 Hz
3. 448 Hz
4. 350 Hz