﻿ Medical Entrance Exam Question and Answers | Electromagnetic Waves - Zigya

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# Electromagnetic Waves

#### Multiple Choice Questions

1.

The electric field associated with an electromagnetic wave in vacuum is given by E=i 40 cos (kz-6x108t), where E, z= and t are in volt/m, metre and second respectively. The value of wave vector k is

• 2 m-1

• 0.5 m-1

• 6 m-1

• 6 m-1

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2.

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

• the frequency of the microwave must match the resonant frequency of the water molecules

• the frequency of the microwave has no relation  with natural frequency of water molecules

• microwave are heat waves, so always produce heating

• microwave are heat waves, so always produce heating

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3.

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

• gamma rays, ultraviolet, infrared, microwaves

• microwaves, gamma rays, infrared, ultraviolet

• infrared, microwave, ultraviolet, gamma rays.

• infrared, microwave, ultraviolet, gamma rays.

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4.

The energy of the EM waves is of the order of 15 keV. To which part of the spectrum does it belong?

• X - rays

• infrared rays

• Ultraviolet rays

• Ultraviolet rays

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5.

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

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6.

The electric and magnetic field of an electromagnetic wave are:

• in phase and parallel to each other

• in opposite phase and perpendicular to each other

• in opposite phase and parallel to each other

• in opposite phase and parallel to each other

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7.

X-rays are

• stream of electron

• stream of proton

• stream of uncharged particle

8.

Who discovered X-rays?

• Roentgen

• Rutherford

•  All of these

9.

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

10.

In gamma ray emission from a nucleus

• both the neutron number and the proton number change

• there is no change in the proton number and the neutron number

• only the neutron number changes

• only the proton number changes