Electromagnetic Waves

The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is

1. microwave, infrared, ultraviolet, gamma rays
2. gamma rays, ultraviolet, infrared, microwaves
3. microwaves, gamma rays, infrared, ultraviolet
4. infrared, microwave, ultraviolet, gamma rays

The electric field of an electromagnetic wave in free space is given by E = 10 (107t + kx ) j V/m, where t and x are in seconds and metres respectively. It can be inferred that Which one of the following pairs of statements is correct ?

1. C and D only
2. A and B only
3. B and C only
4. A and C only

Which of the following statements is false for the properties of electromagnetic waves?

1. Both electric and magnetic field vectors attain the maxima and minima at the same place and same time.
2. The energy in electromagnetic wave is divided equally between electric and magnetic vectors.
3. Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
4. These waves do not require any material medium for propagation.

The electric field part of an electromagnetic wave in a medium is represented by Ex = 0; Ey = 2.5 NC [ (2 106 rads )t - ( 10-2 radm )x ]; Ez = 0. The wave is

1. moving along x direction with frequency 106 Hz and wavelength 100 m.
2. moving along x direction with frequency 106 Hz and wavelength 200 m.
3. moving along -x direction with frequency 106 Hz and wavelength 200 m.
4. moving along y direction with frequency 2 106 Hz and wavelength 200 m.

The velocity of electromagnetic radiation in a medium of permittivity 0 and permeability 0 is given by

1. 1 0 0
2. 0 0
3. 0 0
4. 0 0

The electric and magnetic field of an electromagnetic wave are

1. in opposite phase and perpendicular to each other
2. in opposite phase and parallel to each other
3. in phase and perpendicular to each other
4. in phase and parallel to each other

If v, x and m represent the wavelengths of visible light, X-rays and microwaves respectively, then

1. m > x > v
2. m > v > x
3. v > x > m
4. v > m > x

We consider the radiation emitted by the human body. Which one of the following statements is true?

1. The radiation emitted is in the infra-red region
2. The radiation emitted only during the day
3. The radiation is emitted during the summers and absorbed during the winters
4. The radiation emitted lies in the ultraviolet region and hence is not visible

Which of the following rays are not electromagnetic waves?

1. X-rays
2. -rays
3. -rays
4. heat rays

The velocity of electromagnetic wave is parallel to

1. B E
2. E B
3. E
4. B

What is the cause of greenhouse effect?

1. infra-red rays
2. ultra violet rays
3. X-rays
4. radio waves.

Biological importance of ozone layer is

1. it stops ultraviolet rays
2. ozone layer reduces greenhouse effect
3. ozone layer reflects radio waves
4. ozone layer controls O2/H2 ratio in atmosphere

The frequency order for -rays (a), X-rays (b), UV rays (c) is

1. b > a > c
2. a > b > c
3. c > b > a
4. a > c > b