TextBook Solutions for Board of High School and Intermediate Education Uttar Pradesh Class 12 Physics Physics Part Ii Chapter 15 Communication Systems

Which mode of propagation is used by short wave broadcast services?

A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%.

Give three reasons why the modulation of a message signal is necessary for long-distance transmission.

Show graphically an audio signal, a carrier wave and an amplitude modulated wave.

A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

• 1000

• 10000

• 10

• 100

In a full wave rectifier circuit operating from 50 Hz mains frequency, the fundamental frequency in the ripple would be

• 50 Hz

• 25 Hz

• 100 Hz

• 70.7 Hz

A telephonic communication service is working at carrier frequency of 10 GHz. Only 10% of it is utilized for transmission. How many telephonic channels can be transmitted simultaneously if each channel requires a bandwidth of 5 kHz?

• 2 x 10⁶

• 2 x 10⁵

• 2 x 10⁴

• 2 x 10⁵

A source emits electromagnetic waves of wavelength 3m. One beam reaches the observer directly and other after reflection from a water surface, travelling 1.5 m extra distance and with an intensity reduced to 1/4 as compared to intensity due to the direct beam alone. The resultant intensity will be.

• (1/4) fold

• (3/4) fold

• (5/4) fold

• (9/4) fold

A sound absorber attenuates the sound level by 20 dB. The intensity decreases by a factor of

• 1000

• 10000

• 10

• 100

What maximum frequency can be reflected from ionosphere?

• 5 MHz

• 6 GHz

• 5 KHz

• 500 MHz