Electromagnetic Waves - Live Session - NEET 2020Contact Number: 9667591930 / 8527521718

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1.

Ozone layer blocks the radiations of wave length

(1) Less than $3\times {10}^{-7}m.$

(2) Equal to $3\times {10}^{-7}m.$

(3) More than $3\times {10}^{-7}m.$

(4) All of the above

2.

The wavelength of light of frequency 100 Hz is

(1) $2\times {10}^{6}m$

(2) $3\times {10}^{6}m$

(3) $4\times {10}^{6}m$

(4) $5\times {10}^{6}m$

3.

The frequency of y - rays, X - rays and ultraviolet rays are a, b and c respectively. Then

(1) a > b > c

(2) a < b < c

(3) a = b = c

(4) a > c > b

4.

Ozone layer in atmosphere is useful, because it

(1) stops ultraviolet radiation

(2) absorbs pollutant gase

(3) stops greenhouse effect

(4) stops increase in temperature of atmoshphere

5.

Which is having a minimum wavelength?

(1) X-rays

(2) Ultraviolet rays

(3) y-rays

(4) Cosmic rays

6.

What is the cause of the 'Greenhouse effect'?

(1) Infrared rays

(2) Ultraviolet rays

(3) X-rays

(4) Radio waves

7.

The velocity of the electromagnetic wave is parallel to

(1) $\overrightarrow{B}\times \overrightarrow{E}$

(2) $\overrightarrow{E}\times \overrightarrow{B}$

(3) $\overrightarrow{E}$

(4) $\overrightarrow{B}$

8.

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

(1) The radiation emitted is in the infrared region

(2) The radiation is 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

9.

Which of the following ray are not electromagnetic waves?

(1) X-rays

(2) y-rays

(3) $\beta $-rays

(4) Heat rays

10.

If ${\lambda}_{v},{\lambda}_{x},and{\lambda}_{m}$ represent the wavelength of visible light, X-rays and microwaves respectively, then

(1) ${\lambda}_{m}>{\lambda}_{x}>{\lambda}_{v}$

(2) ${\lambda}_{v}>{\lambda}_{m}>{\lambda}_{x}$

(3) ${\lambda}_{v}>{\lambda}_{x}>{\lambda}_{m}$

(4) ${\lambda}_{m}>{\lambda}_{v}>{\lambda}_{x}$

11.

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

12.

The velocity of electromagnetic radiation in a medium of permittivity ${\epsilon}_{0}$ and permeability ${\mu}_{0}$ is given by

(1) $\sqrt{\frac{{\mu}_{0}}{{\epsilon}_{0}}}$

(2) $\sqrt{\frac{{\epsilon}_{0}}{{\mu}_{0}}}$

(3) $\sqrt{{\mu}_{0}{\epsilon}_{0}}$

(4) $\frac{1}{\sqrt{{\mu}_{0}{\epsilon}_{0}}}$

13.

The electric field part of an electromagnetic wave in a medium is represented by ${E}_{x}=0;$

${E}_{y}=2.5\frac{N}{C}\mathrm{cos}\left[\left(2\mathrm{\pi}\times {10}^{6}\frac{\mathrm{rad}}{\mathrm{s}}\right)t-\left(\mathrm{\pi}\times {10}^{-2}\frac{\mathrm{rad}}{\mathrm{m}}\right)x\right];{E}_{z}=0$

The wave is

(1) moving along x-direction with frequency ${10}^{6}$ Hz and wavelength 100 m

(2) moving along x-direction with frequency ${10}^{6}$ Hz and wavelength 200 m

(3) moving along $-x$-direction with frequency ${10}^{6}$ Hz and wavelength 200 m

(4) moving along y-direction with frequency $2\mathrm{\pi}\times {10}^{6}$ Hz and wavelength 200 m.

14.

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

(1) These waves do not require any material medium for propagation.

(2) Both electric and magnetic field vectors attains the maxima and minima at the same place and same time.

(3) The energy in electromagnetic wave is divided equally between electric and magnetic vectors.

(4) Both electric and magnetic field are parallel to each other and perpendicular to the direction of propagation of wave.

15.

The electric field of an electromagnetic wave in free space is given by:

$\overrightarrow{E}=10\mathrm{cos}({10}^{7}t+kx)\stackrel{\wedge}{j}V{m}^{-1}$, where, t and x are in seconds and metres, respectively. It can be inferred that

(a) The wave length $\lambda $is 188 4 m

(b) The wave number k is 0.33 rad ${m}^{-1}$

(c) The wave amplitute is 10 V ${m}^{-1}$

(d) The wave is propagating along +x direction

Which one of the following pairs of statements is correct?

(1) (a) and (b)

(2) (b) and (c)

(3) (a) and (c)

(4) (c) and (d)

16.

The electric and the magnetic field, associated with an electromagnetic wave, propagating along the +z -axis, can be represented by

(1) $\left[\overrightarrow{E}={E}_{0}\hat{j},\overrightarrow{B}={B}_{0}\hat{k}\right]$

(2) $\left[\overrightarrow{E}={E}_{0}\hat{i},\overrightarrow{B}={B}_{0}\hat{j}\right]$

(3) $\left[\overrightarrow{E}={E}_{0}\hat{k},\overrightarrow{B}={B}_{0}i\right]$

(4) $\left[\overrightarrow{E}={E}_{0}\hat{j},\overrightarrow{B}={B}_{0}\hat{i}\right]$

17.

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

(1) infrared, microwave, ultraviolet, gamma rays.

(2) microwave, infrared, ultraviolet, gamma rays.

(3) gamma rays, ultraviolet, infrared, microwaves.

(4) microwaves, gamma rays, infrared, ultraviolet.

18.

$TheelectricfieldassociatedwithanE.M.waveinvaccumisgivenby\phantom{\rule{0ex}{0ex}}\overrightarrow{E}=\hat{i}40\mathrm{cos}(kz-6\times {10}^{8}t),whereE,zandtareinV{m}^{-1},mands,respectively.\phantom{\rule{0ex}{0ex}}Thevalueofwavevectorkis$

(1) 2 ${m}^{-1}$

(2) 0.5 ${m}^{-1}$

(3) 6 ${m}^{-1}$

(4) 3 ${m}^{-1}$

19.

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to

(1) the ratio of magnetic permeability to the electric susceptibility of vaccum.

(2) unity

(3) the speed of light in vacuum

(4) reciprocal of speed of light in vacuum

20.

The condition under which a microwave oven heats up a food item containing water molecules most efficiently is

(1) the frequency of the microwaves must match the resonant frequency of the water molecules.

(2) the frequency of the microwaves has no relation with natural frequency of water molecules.

(3) microwaves are heat waves, so always produce heating

(4) infra-red waves produce heating in a microwave oven.

21.

Out of the following options, which one can be used to produce a propagating electromagnetic wave ?

(1) A chargeless particle

(2) An accelerating charge

(3) A change moving at constant velocity

(4) A stationary charge

22.

In an electromagnetic wave in free space, the root mean square value of the electric field is ${E}_{rms}=6V/m$. The peak value of the magnetic field is

(1) $2.83\times {10}^{-8}T$

(2) $0.70\times {10}^{-8}T$

(3) $4.23\times {10}^{-8}T$

(4) $1.41\times {10}^{-8}T$

23.

An em was is propagating in a medium with a velocity $\overrightarrow{V}=V\hat{i}$. The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along

(1) $-ydirection$

(2) $+zdirection$

(3) $-zdirection$

(4) $-xdirection$

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