# Oscillations and Waves (NEET Physics): Questions 171 - 174 of 195

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## Question number: 171

» Oscillations and Waves » Beats

Assertion-Reason▾

### Assertion (Ꭺ)

Beats cannot be produced by light sources.

### Reason (Ꭱ)

Light sources have constant phase difference.

### Choices

Choice (4) Response

a.

Ꭺ is true but Ꭱ is false

b.

Ꭺ is false but Ꭱ is true

c.

Both Ꭺ and Ꭱ are true but Ꭱ is NOT the correct explanation of Ꭺ

d.

Both Ꭺ and Ꭱ are true and Ꭱ is the correct explanation of Ꭺ

## Question number: 172

» Oscillations and Waves » Doppler Effect in Sound

MCQ▾

### Question

The speed of sound in air at a given temperature is 250 m/s. An engine blows whistle at a frequency of 810 cps. It is approaching the observer with velocity 25 m/s. The apparent frequency in cps heard by the observer will be

### Choices

Choice (4) Response

a.

1100

b.

800

c.

900

d.

1000

## Question number: 173

» Oscillations and Waves » Beats

MCQ▾

### Question

A source of sound of frequency 233 Hz is moving rapidly towards a wall with a velocity of 3.5 m/s. The speed of sound is 330 m/s. If the observer is between the wall and the source, then the beats heard per second will be,

### Choices

Choice (4) Response

a.

4.2 Hz

b.

5.3 Hz

c.

4.9 Hz

d.

Zero

## Question number: 174

» Oscillations and Waves » Beats

MCQ▾

### Question

A sound wave of frequency travels horizontally to the right. It is reflected from a large vertical plane surface moving to the left with a speed V. The speed of sound in the medium is c.

### Choices

Choice (4) Response

a.

The number of beats hears by a stationary listener to the left of the reflecting surface is

b.

The frequency of the reflected wave is

c.

The number of waves striking the surface per second is

d.

The wavelength of the reflected wave is

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