A second harmonic has to be generated in a string of length l stretched between two rigid supports. Distances from one end where the string has to be plucked and touched are :

(1) Plucked at $\frac{l}{4}$ and touched at $\frac{l}{2}$

(2) Plucked at $\frac{l}{4}$ and touched at $\frac{3l}{4}$

(3) Plucked at $\frac{l}{2}$ and touched at $\frac{l}{4}$

(4) Plucked at $\frac{l}{2}$ and touched at $\frac{3l}{4}$

A tube closed at one end and containing air is excited. It produces the fundamental note of frequency of 512 Hz. If the same tube is open at both the ends the fundamental frequency that can be produced is :

(1) 1024 Hz

(2) 512 Hz

(3) 256 Hz

(4) 128 Hz

An empty vessel is getting filled with water, then the frequency of vibration of the air column in the vessel 

(1) Remains the same

(2) Decreases

(3) Increases

(4) First increases then decrease

If the velocity of sound in air is 336 m/s. The maximum length of a closed pipe that would produce a just audible sound will be : 

(1) 3.2 cm

(2) 4.2 m

(3) 4.2 cm

(4) 3.2 m

The frequency of fundamental tone in an open organ pipe of length 0.48 m is 320 Hz. The speed of sound is 320 m/sec. Frequency of fundamental tone in closed organ pipe will be : 

1. 153.8 Hz

2. 160.0 Hz

3. 320.0 Hz

4. 143.2 Hz

An open pipe of length l vibrates in the fundamental mode. The pressure variation is maximum at :

(1) l/4 from ends

(2) The middle of the pipe

(3) The ends of the pipe

(4) At l/8 from ends of pipe

In one metre long open pipe what is the harmonic of resonance obtained with a tuning fork of frequency 480 Hz : (Velocity of sound: 320 m/s)

(1) First

(2) Second

(3) Third

(4) Fourth

The frequency of a whistle of an engine is 600 cycles/sec is moving with the speed of 30 m/sec towards an observer. The apparent frequency will be (velocity of sound = 330 m/s) 

(1) 600 cps

(2) 660 cps

(3) 990 cps

(4) 330 cps

A source of sound is moving with constant velocity of 20 m/s emitting a note of frequency 1000 Hz. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him will be

(1) 9 : 8

(2) 8 : 9

(3) 1 : 1

(4) 9 : 10

(Speed of sound v = 340 m/s)

A source emits a sound of frequency of 400 Hz, but the listener hears it to be 390 Hz. Then 

(1) The listener is moving towards the source

(2) The source is moving towards the listener

(3) The listener is moving away from the source

(4) The listener has a defective ear