# +2 Physics Unit 10 - Communication Systems

8 Questions | Total Attempts: 2199

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Prepared by P. ILAIYARAJA M. Sc. ,B. Ed. , PG ASST IN PHYSICS , GHSS, PANCHANATHIKKULAM EAST, NAGAI DT.   ; & www. Padasalai. Net

• 1.
High frequency waves follow
• A.

Ionospheric propagation

• B.

The curvature of the earth

• C.

The ground wave propagation

• D.

The line of sight direction

• 2.
The main purpose of modulation is to
• A.

transmit low frequency information over long distances efficiently

• B.

Produce side bands

• C.

Acquire wave shaping of the carrier wave

• D.

Combine two waves of different frequencies

• 3.
In amplitude modulation
• A.

The amplitude of the carrier wave varies in accordance with the amplitude of the modulating signal.

• B.

The amplitude of the carrier wave remains constant

• C.

The amplitude of the carrier varies in accordance with the frequency of the modulating signal

• D.

Modulating frequency lies in the audio range

• 4.
In amplitude modulation, the band width is
• A.

Twice the signal frequency

• B.

Thrice the signal frequency

• C.

Four times the signal frequency

• D.

Equal to the signal frequency

• 5.
In phase modulation
• A.

Both the phase and the frequency of the carrier wave varies.

• B.

There is no change in the frequency and phase of the carrier wave

• C.

Only the phase of the carrier wave varies

• D.

Only the frequency of the carrier wave varies.

• 6.
The RF channel in a radio transmitter produces
• A.

High frequency carrier waves

• B.

both audio signal and high frequency carrier waves

• C.

Low frequency carrier waves.

• D.

Audio signals

• 7.
The purpose of dividing each frame into two fields so as to transmit 50 views of the picture per second is
• A.

To avoid flicker in the picture

• B.

The fact that handling of higher frequencies is easier

• C.

that 50 Hz is the power line frequency in India

• D.

To avoid unwanted noises in the signals

• 8.
Printed documents to be transmitted by fax are converted into electrical signals by the process of
• A.

Scanning

• B.

modulation

• C.

Light variation

• D.

Reflection

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