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Waves

Multiple Choice Questions

61.
Two closed organ pipes of length 100 cm and 101 cm produces 16 beats in 20 sec. When each pipe is sounded in its fundamental mode. Calculate the velocity of sound.

303 ms^-1

332 ms^-1

323.2 ms^-1

300 ms^-1yes

323.2 ms^-1

Frequency of fundamental mode of vibrations of 1^st closed organ pipe,

ν₁ = $\frac{ν}{4 l_{1}}$

ν₁ = $\frac{ν}{4 \times 100}$ ....(i)

Frequency of fundamental mode of vibrations of 2^nd closed organ pipe,

ν₂ = $\frac{ν}{4 l_{2}}$

ν₂ = $\frac{ν}{4 \times 101}$ ....(ii)

As in question

ν₁ $-$ ν₂ = $\frac{16}{20}$

⇒ $\frac{ν}{4 \times 100} - \frac{ν}{4 \times 101} = \frac{16}{20}$

⇒ $\frac{ν}{4} [\frac{101 - 100}{101}] = \frac{16}{20}$

⇒ $\frac{ν}{4} \times \frac{1}{101} = \frac{16}{20}$

⇒ ν = $\frac{16 \times 101 \times 4}{20}$

⇒ ν = 323.2 ms^-¹

62.

A siren emitting sound of frequency 800 Hz is going away from a static listener with a speed of 30 m/s. The frequency of sound heard by listener is ( velocity of sound = 300 m/s )

727.3 Hz
481.2 Hz
644.8 Hz
286.5 Hz

63.

Assertion: Sound waves cannot travel in vacuum but light can travel in vacuum.

Reason: Sound waves are longitudinal waves and they cannot be polarised but electromagnetic waves are transverse and they can be polarised.

If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false

64.

A stone thrown into still water, creates a circular wave pattern moving radially outwards. Ifr is the distance measured from the centre of the pattern, the amplitude of the wave varies as

r^1/2
r^-1
r²
r^3/2

65.

Which of the following diagrams represents the variation of electric field vector with time for a circularly polarized light?

66.

When a guitar string is sounded with a 440 Hz tuning fork, a beat frequency of 5 Hz is heard. If the experiment is repeated with a tuning fork of 437 Hz, the beat frequency is 8 Hz. The string frequency (Hz) is

67.

For a wave propagating in a medium, identify the property that is independent of the others.

Velocity
Wavelength
Frequency
All these depend on each other

68.

The waves produced by a motorboat sailing in water are

transverse
longitudinal
longitudinal and transverse
stationary

69.

Two springs are connected to a block mass M placed on a frictionless surface as shown in figure. If both the springs have a spring constant k, the frequency of oscillation of the block is

70.

An organ pipe closed at one end has a fundamental frequency of 1500 Hz. The maximum number of overtones generated by this pipe which a normal can hear is

Previous Year Papers

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Multiple Choice Questions

61. Two closed organ pipes of length 100 cm and 101 cm produces 16 beats in 20 sec. When each pipe is sounded in its fundamental mode. Calculate the velocity of sound. 303 ms-1 332 ms-1 323.2 ms-1 300 ms-1yes

61.
Two closed organ pipes of length 100 cm and 101 cm produces 16 beats in 20 sec. When each pipe is sounded in its fundamental mode. Calculate the velocity of sound.

303 ms^-1

332 ms^-1

323.2 ms^-1

300 ms^-1yes