# modern and space physics, sources of energy - Category wise Question and Answer Practice Test with Solutions

#### modern and space physics, sources of energy PRACTICE TEST [3 - EXERCISES]

Question : 1

The process of superimposing signal frequency (i.e., audio wave) on the carrier wave is known as

a) Reception

b) Modulation

c) Transmission

d) Detection

Question : 2

The service area of space wave communication increases by –

a) Decreasing the height of receiving antenna

b) Increasing the height of both transmitting and receiving antenna

c) Increasing the height of transmitting antenna

d) Decreasing the distance between transmitting and receiving antenna

Maximum range of space wave propagation

d = $4/3\text" x 1.23 "[√{H_t}+√{H_r}]$

⇒ d ∝ Ht and d ∝ Hr

∴ d increases if Ht and Hr

i.e. height of transmitting and receiving antenna increases.

Question : 3

In frequency modulation:

a) The frequency of modulated wave varies as amplitude of modulating wave

b) The amplitude of modulated wave varies as amplitude of carrier wave

c) The amplitude of modulated wave varies as frequency of carrier wave

d) The frequency of modulated wave varies as frequency of modulating wave.

The process of changing the frequency of a carrier wave (modulated wave) in accordance with the audio frequency signal (modulating wave) is known as frequency modulation (FM).

Question : 4 [CDS]

Light Emitting Diode (LED) converts

a) electrical energy into light energy

b) thermal energy into light energy

c) light energy into electrical energy

d) mechanical energy into electrical energy

Question : 5

At absolute zero, Si acts as

a) metal

b) insulator

c) non-metal

d) None of these

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