Radiowaves

Q.

What are the applications of amplitude modulation?

Q.

Which radiation is used for satellite communication?

1. Infrared rays

2. Gamma rays

3. Radio waves

4. X - Rays

Q.

How are microwaves produced? Why is it necessary in microwave ovens to select the frequency of microwaves to match the resonant frequency of water molecules?

Q.

Which kind of waves are used in sonography?

1. Infrared waves

2. Micro waves

3. Sound waves

4. Ultrasonic waves

Q.

Microwave oven act on which principle?

1. Giving rotational energy to water molecules

2. Giving translational energy to water molecules

3. Giving vibrational energy to water molecules

4. Transferring electrons from lower to higher energy levels in water molecules

Q.

Name the radioactive radiations which have the least penetrating power.

Q.

Does wavelength change after diffraction?

Q.

A radio transmitter operates at a frequency of 880 kHz and a power of 10 kW. The number of photons emitted per second is

Q.

The waves relevant to telecommunication are

1. Visible light

2. Infrared

3. Ultraviolet

4. Microwave

5. None of the above

Q.

In light modulation, which characteristic of the carrier light wave is varied?

1. Amplitude

2. Frequency

3. Phase

4. Intensity

Q.

What is the difference between analog and digital signal?

Q.

Why amplitude modulation is used for long-distance communication?

Q.

The ratio of energy to frequency of electromagnetic radiation is equal to ______ .

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. Infrared radiations are used in

1. Microwave ovens
2. Long distance photography
3. Microscopes
4. Treatment of cancer

Q. The radio waves of frequency 30 MHz to 300 MHz belong to:

1. very high frequency band
2. high frequency band
3. ultra high frequency band
4. super high frequency band.

Q. The maximum frequency of transmitted radio waves above which the radio waves are no longer reflected back by ionosphere is ................. (N = maximum electron density of ionosphere, g = acceleration due to gravity)

1. $g{N}^2$
2. $gN$
3. $g^2{N}^2$
4. $g\sqrt{N}$

Q.

The speed of a wave in a certain medium is 960 m/s. If 3600 waves pass over a certain point of the medium in 1 minute, the wavelength is ___.

1. 2 m

2. 4 m

3. 8 m

4. 16 m

Q. Assertion :Radio waves are diffracted by buildings. Reason: Radio waves are high energy waves.

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

Q. Maximum diffraction takes place in a given slit for

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

Q. Assertion :Radio waves can be polarised. Reason: Sound waves in air are longitudinal in nature.

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

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

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. Complete the following passage(s) with an appropriate word/term to be filled in the blank spaces.
Troposphere, Stratosphere, Triatomic, Ozonosphere, Ozone shield, Diatomic, Ozone, Equator, Poles, Reactive.
Ozone is a __(1)__molecule made up of three atoms of oxygen, $O_3$. The normal oxygen molecule is __(2)__. Oxygen is essential for all aerobic forms and combustion activities. __(3)__ is a deadly poison. Very little of it is present in the lower part of the atmosphere called __(4)__. A good quantity of ozone is present in the stratum of the atmosphere called __(5)__. It lies above the troposphere and extends between 16-50 km of height above __(6)__ and 8-30 km above __(7)__. Here, it is formed in situ from oxygen by the action of high energy ultraviolet rays. The latter split some oxygen molecules into nascent or atomic oxygen (O). Atomic oxygen is highly __(8)__. It combines with ($O_2$) to form ozone. The area of the stratosphere which is rich in ozone is called the ozone layer or ____(9)____. It is also called __(10) __.

Q. For treating arthritis

1. radio waves are used
2. direct current is used
3. mircowaves are used
4. AC of high frequency is used

Q. Radio waves of constant amplitude can be generated with:

1. Filter
2. Rectifier
3. FET
4. Oscillator

Q.

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

Q. Microwaves and radio waves can propagate in vacuum.

1. True
2. False

Q. Answer the following questions .
Long - distance radio brodcasts use shorts -wave bands , Why ?