Radiowaves

Q.

Which radiation is used for satellite communication?

1. Infrared rays

2. Gamma rays

3. Radio waves

4. X - Rays

Q. Answer the following questions: (a) Long distance radio broadcasts use short-wave bands. Why? (b) It is necessary to use satellites for long distance TV transmission. Why? (c) Optical and radiotelescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth.Why? (d) The small ozone layer on top of the stratosphere is crucial for human survival. Why? (e) If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now? (f ) Some scientists have predicted that a global nuclear war on the earth would be followed by a severe ‘nuclear winter’ with a devastating effect on life on earth. What might be the basis of this prediction?

Q. International broadcasting requires.

1. Medium frequency radio waves
2. High frequency radio waves
3. Low frequency radio waves
4. Longitudinal waves

Q. Radio waves travel with a speed of.

1. $3\times {10}^8$ m/sec
2. $3\times {10}^7$ m/sec
3. $3\times {10}^6$ m/sec
4. $3\times {10}^9$ m/sec

Q. TV waves have a wavelength range of $1-10$ meter. Their frequency range in $MHz$ is

1. $3-30$
2. $30-300$
3. $300-3000$
4. $3-3000$

Q. Radio waves of constant amplitude can be generated with

1. rectifier
2. filter
3. oscillator
4. F.E.T

Q. Astronauts communicate with one another on moon with the help of.

1. radio waves
2. sound waves
3. ultrasound waves
4. infrasound waves

Q. Maximum diffraction takes place in a given slit for

1. $\gamma$-rays
2. Ultraviolet light
3. Radio waves
4. Infrared light

Q. Microwaves and radio waves can propagate in vacuum.

1. True
2. False

Q. Assertion :Short wave bands are used for transmission of radio waves to a large distance Reason: Short waves are reflected by ionosphere

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect