# Communication System (NEET (NTA-National Eligibility cum Medical Entrance Test) Physics): Questions 25 - 29 of 42

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## Question number: 25

» Communication System » Sky and Space Wave Propagation

MCQ▾

### Question

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

### Choices

Choice (4) Response

a.

175 MHz

b.

190 MHz

c.

150 MHz

d.

170 MHz

## Question number: 26

» Communication System » Propagation of Electromagnetic Waves in the Atmosphere

MCQ▾

### Question

In short wave communication which of the following frequencies will be reflected back by the ionosphere layer, having electron density 10 11 per m 3

### Choices

Choice (4) Response

a.

18.1 MHz

b.

10.42 MHz

c.

12.24 MHz

d.

2.84 MHz

## Question number: 27

» Communication System » Sky and Space Wave Propagation

MCQ▾

### Question

For sky wave propagation of a 10 MHz signal, what should be the minimum electron density in ionosphere,

### Choices

Choice (4) Response

a.

b.

c.

d.

## Question number: 28

» Communication System » Amplitude and Frequency Modulation

MCQ▾

### Question

In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be,

### Choices

Choice (4) Response

a.

500 cycles/sec

b.

50, 000 cycles/sec

c.

50 cycles/sec

d.

100 cycles/sec

## Question number: 29

» Communication System » Propagation of Electromagnetic Waves in the Atmosphere

Assertion-Reason▾

### Assertion (Ꭺ)

Television signals are not received through sky-wave propagation.

### Reason (Ꭱ)

The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.

### Choices

Choice (4) Response

a.

Ꭺ is true but Ꭱ is false

b.

Both Ꭺ and Ꭱ are false

c.

Ꭺ is false but Ꭱ is true

d.

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

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