Tag: electromagnetic waves

Questions Related to electromagnetic waves

Choose the correct answer from the alternatives given.
Radio waves diffract around building although light waves do not. The reason is that radio waves

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. travel with speed larger than c

  2. have much larger wavelength than light

  3. are not electromagnetic waves

  4. None of these

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Correct Option: B
Explanation:

$Answer:-$ B

Both radio and light waves are EM waves, just in different frequency ranges. The wavelength of visible light is typically around the 600 nm range, which is 6/1000 of a millimeter (very small!). Radio waves on the other hand, often wave wavelengths of a few yards long. For a wave to diffract around an object, the size of the object must be on the same order of the wavelength of the wave.

Which of the following electromagnetic wave play an important role in maintaining the earths warmth or average temperature through the greenhouse effect? 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Visible rays

  2. Infrared waves

  3. Gamma rays

  4. Ultraviolet rays

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Correct Option: B
Explanation:

Infrared radiation play an important role in maintaining the earths warmth or average temperature through the greenhouse effect.

The correct option is B.

The waves used by artificial satellites for communication is the

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. microwaves

  2. infrared waves

  3. radio waves

  4. X-rays

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Correct Option: A
Explanation:

The microwaves are preferred in order to communicate with the artificial satellites which are orbiting the earth at a particular height from the surface of the earth. The microwaves are preferred because they can penetrate through the Earth's atmosphere very easily and reach the target satellite.

Choose the correct answer from alternatives given.
The phenomena involved in the reflection of radio waves by ionosphere is similar to

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. reflection of light by a plane mirror.

  2. total internal reflection of light in air during a mirage.

  3. dispersion of light by water molecules during the formation of a rainbow.

  4. scattering of light by the particles of air.

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Correct Option: C
Explanation:

The phenomenon involved in the reflection of radiowaves by ionosphere is similar to total internal reflection of light in air during a mirage (angle of incidence gt critical angle). It is same as the formation of the rainbow because it also involves the process of total internal reflection.


Choice $(b)$ is correct.

If $v _{g}, v _{x}$, and $v _{m}$ are speeds of gamma rays, $X$ rays, and microwaves respectively in vacuum, then:

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. $V _{g} < V _{x} < V _{m}$

  2. $V _{g}>V _{x}>V _{m}$

  3. $V _{g} < V _{x}> V _{m}$

  4. $V _{g}=V _{x}=V _{m}$

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Correct Option: D
Explanation:
The gamma rays, $X-$ rays and the microwaves are the Electromagnetic waves and the speed of all the electromagnetic waves remains the same in vacuum irrespective of other parameters. All will travel at the speed of light.

$V _{g}=V _{x}=V _{m}$ 

 The speed of Electromagnetic waves is always the same in vacuum. So, option $(D)$ is correct.

Which of the following electromagnetic waves is used in medicine to destroy cancer cell?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. IR- rays

  2. Visible rays

  3. Gamma rays

  4. Ultraviolet rays

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Correct Option: C
Explanation:
Gamma rays are dominantly used in medicines to destroy the cells that are cancer affected. The gamma rays are chosen such that its energy does not harm the healthy cells.

Therefore, the rays used in medicine to destroy cancer cells are Gamma rays.

A. wavelength of microwave is greater than that of ultraviolet rays.
B. The wave length of infrared rays is lesser than that of ultraviolet rays.
C. wavelength of microwave is lesser than that of ultraviolet rays
D. Gamma rays has shortest wavelength in the electromagnetic spectrum.
Choose the correct option from the given options.

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. A and B are true

  2. B and C are true

  3. C and D are true

  4. A and D are true

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Correct Option: D
Explanation:
The wavelength and the frequency of the Electromagnetic waves are inversely proportional to each other.

$A$. The wavelength of Microwave is greater than UV rays.
The frequency of the microwave is less than that of the Ultraviolet rays, the wavelength of the Microwaves will be longer than the Ultraviolter rays.

$D$. Gamma rays have the shortest wavelength in the EM spectrum.
The frequency of the gamma rays is the highest in the electromagnetic spectrum. So, it will have the shortest wavelength.

The wavelength of the infrared is higher than the Ultraviolet rays and also the wavelength of the microwave is higher than Ultraviolet rays. So, options $B$ and $C$ are not true.
Option $(D)$ is correct.

Which of the following is absorbed by the ozone layer ?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. only gamma rays

  2. visible light

  3. radio waves

  4. ultraviolet

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Correct Option: D
Explanation:

Ozone is a molecule made of three oxygen atom or $O _3$. When ultraviolet light in the range $240nm$ and $320 nm$ strikes an ozone molecule, it absorbs the energy and the $O _3$ changes to $O _2$ and $O$. The $O$ atom soon combines with another $O _2$ molecule to form $O _3$ and is ready to absorb ultra violet light.

Which wavelength of sun is used finally as electric energy? 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Radio waves

  2. Infrared waves

  3. Visible light

  4. Micro waves

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Correct Option: B
Explanation:

The heating property of Infra red waves is used in solar heater and solar cells, Hence option (b) is correct. 

What is the type of invisible radiation from space that can be detected from Earth's surface?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Gamma rays

  2. X-rays

  3. Infrared radiation

  4. Radio waves

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Correct Option: A