# Communication System (NEET (NTA)-National Eligibility cum Entrance Test (Medical) Physics): Questions 18 - 24 of 42

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## Question number: 18

» Communication System » Need for Modulation

MCQ▾

### Question

An oscillator is producing FM waves of frequency 4 kHz and modulating index is 8. Thus calculate the variation.

### Choices

Choice (4) Response

a.

5.0

b.

0.20

c.

0.67

d.

1.5

## Question number: 19

» Communication System » Basic Elements of Communication System

MCQ▾

### Question

The phenomenon by which light travels in an optical fibers

### Choices

Choice (4) Response

a.

Transmission

b.

Total internal reflection

c.

Refraction

d.

Re-reflection

## Question number: 20

» Communication System » Sky and Space Wave Propagation

MCQ▾

### Question

Maximum usable frequency (MUF) in F-region layer is x, when the critical frequency is 55 MHz and the angle of incidence is 60°. Then x is (cos 70° = 0.34)

### Choices

Choice (4) Response

a.

120 MHz

b.

110 MHz

c.

109 MHz

d.

150 MHz

## Passage

The electron density of a layer of ionosphere at a height 150 km from the earth’s surface is 9 ⨯ 10 9 per m 3. For the sky transmission from this layer up to a range of 250 km,

## Question number: 21 (1 of 3 Based on Passage) Show Passage

» Communication System » Bandwidth of Signals

MCQ▾

### Question

Maximum usable frequency is,

### Choices

Choice (4) Response

a.

3.5 Hz

b.

3.5 ⨯ 10 6 HZ

c.

3.5 ⨯ 10 10 Hz

d.

3.5 ⨯ 10 3 Hz

## Question number: 22 (2 of 3 Based on Passage) Show Passage

» Communication System » Basic Elements of Communication System

MCQ▾

### Question

Angle of incidence of this layer is

### Choices

Choice (4) Response

a.

b.

c.

d.

0 0

## Question number: 23 (3 of 3 Based on Passage) Show Passage

» Communication System » Sky and Space Wave Propagation

MCQ▾

### Question

The critical frequency of the layer is

### Choices

Choice (4) Response

a.

2.7 Hz

b.

2 Hz

c.

2.7 MHz

d.

2.78 kHz

## Question number: 24

» Communication System » Amplitude and Frequency Modulation

MCQ▾

### Question

In frequency modulation

### Choices

Choice (4) Response

a.

The amplitude of modulated wave varies as amplitude of carrier wave

b.

The frequency of modulated wave varies as frequency of modulating wave

c.

The amplitude of modulated wave varies as frequency of carrier wave

d.

The frequency of modulated wave varies as amplitude of modulating wave

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