# Physics: Wave Optics MCQs

##### 1. Question

An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

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##### 2. Question

A whistle producing sound waves of frequencies 9500 HZ and above is approaching a stationary person with speed v ms-1 . The velocity of sound in air is 300 ms-1 . If the person can hear frequencies upto a maximum of 10,000 HZ, the maximum value of v upto which he can hear whistle is

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##### 3. Question

A motor cycle starts from rest and accelerates along a straight path at 2m/s 2 . At the starting point of the motor cycle there is a stationary electric siren. How far has the motor cycle gone when the driver hears the frequency of the siren at 94% of its value when the motor cycle was at rest? (Speed of sound = 330 ms-1 )

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##### 4. Question

This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements.

Statement 1: Bats emitting ultrasonic waves can detect the location of a prey by hearing the waves reflected from it.

Statement 2: When the source and the detector are moving, the frequency of reflected waves is changed.

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##### 5. Question

An engine approaches a hill with a constant speed. When it is at a distance of 0.9 km, it blows a whistle whose echo is heard by the driver after 5 seconds. If the speed of sound in air is 330 m/s, then the speed of the engine is :

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