Multiple Choice Questions
Choose the correct alternative. Each question is carrying one mark.
1. According to Maxwell's hypothesis, a changing electric field can give rise to :
- (a) an e.m.f.
- (b) electric current
- (c) magnetic field
- (d) electrical pressure.
- (c) magnetic field
2. The velocity of light in vacuum is :
- (a) √ฦ₀๐₀
- (b) ฦ₀/๐₀
- (c) √ฦ₀/๐₀
- (d) 1/√ฦ₀/๐₀
- (d) 1/√ฦ₀/๐₀
3. Infrared part of electromagnetic spectrum lies in between :
- (a) X-rays and ultraviolet
- (b) visible and microwaves
- (c) ultraviolet and visible
- (d) microwaves and radiowaves.
- (b) visible and microwaves
4. Which of the following is not electromagnetic waves ?
- (a) UV rays
- (b) ๐พ-rays
- (c)๐ฝ -rays
- (d) X-rays.
- (c) ๐ฝ-rays
5. Electric field and magnetic field in electromagnetic waves oscillate:
- (a) in phase with each other
- (b) out of phase with each other
- (c) with phase difference of ๐/2
- (d) parallel to each other.
- (c) with phase difference of ๐/2
6. The dimensions of `\frac{1}{2}`ฦ₀E² ( ฦ₀ permittivity of free space, E = electric field) are :
- (a) (ML T⁻¹ )
- (b) (ML² T⁻² )
- (c) (ML⁻¹ T⁻² )
- (d)(ML² T⁻¹ )
- (c) (ML⁻¹ T⁻² )
7. The Poynting vector is defined as :
- (a) ฤXB
- (b) E.B
- (c) E.H
- (d) E x H
- (a) ฤXH
8. Which rays are emitted by human body
- (a) X ray
- (b) Gamma ray
- (c) Visible rays
- (d) Infrared rays
- (d) Infrared rays
9. For treating muscular sprain, we use:
- (a) IR lamps
- (b) UV lamps
- (c) ordinary lamps
- (d) none of these.
- (a) IR lamps
10. Choose the wrong statement.
- (a) X-rays are used to detect fracture in bones.
- (b) X-rays are of atomic origin.
- (c) X-rays have wavelength of 1 ยตm.
- (d) X-rays were discovered by W. Rontgen.
- (c) X-rays have wavelength of 1 ยตm.
11. In microwave ovens, the frequency of microwaves is .......... resonant frequency of water molecules.
- (a) equal to
- (b) much greater than
- (c) much smaller than
- (d) double of.
- (a) equal to
12. The waves used in telecommunication are
- (a) Micro waves
- (b) Ultraviolet light
- (c) X-rays
- (d) ๐พ-rays
- (a) Micro waves
13. Displacement current is:
- (a) produced when electric flux changes with time
- (b) produced when magnetic flux changes with time
- (c) cannot exist in vacuum
- (d) not a current at all.
- (a) produced when electric flux changes with time
14. Calculate the wavelength of electromagnetic waves of frequency 300 MHz.
- (a) 3 m
- (b) 2 m
- (c) 30 m
- (d) 1 m
- (d) 1 m using formula ๐ =c/๐
15. From which layer of atmosphere, radio waves are reflected ?
- (a) Ionosphere
- (b) Mesosphere
- (c) Chromosphere
- (d) None of there
- (a) Ionosphere
16. The ionosphere can reflect which type of waves ?
- (a) Microwaves
- (b) Radio waves
- (c) X-rays
- (d) ๐ธ-rays
- (b) Radio waves
17. If E and B are the electric and magnetic field vectors of e.m. waves, then the direction of
propagation of e.m. wave is along the direction of :
- (a) E
- (b) B
- (c) E X B
- (d) none of these.
- (c) E X B
18. The speed of electromagnetic wave in a medium is same for :
- (a) odd frequencies
- (b) even frequencies
- (c) all frequencies
- (d) all intensities.
- (c) all frequencies
19. The amplitudes of electric and magnetic fields related to each other are :
- (a) E₀ = B₀
- (b) E₀ = cB₀
- (c) E₀ = B₀/c
- (d) E₀ = c/B₀
- (b) E₀ = cB₀
20. Which of the following has the longest wavelength ?
- (a) Radio waves
- (b) ๐ธ-rays
- (c) Microwaves
- (d) X-rays.
- (a) Radio waves
21. Which of the following electromagnetic waves have smallest wavelength ?
- (a) X-rays
- (b) Radio waves
- (c) Gamma rays
- (d) Microwaves
- (c) Gamma rays
22. Production of electromagnetic waves is demonstrated by :
- (a) Hertz
- (b) Jagdish Chandra Bose
- (c) Marconi
- (d) Huygen
- (a) Hertz
23. Which of the following have shortest frequency?
- (a) microwaves
- (b) visible light
- (c) X-rays.
- (c) ๐-rays
- (a) microwaves
The correct order of decreasing frequencies of em waves is gamma rays> X rays> UV rays> Visible light> Infra red waves> Micro Waves> Radio waves
24. If radio waves have wavelength of 150 m in vacuum, then its frequency is :
- (a) 2 kHz
- (b) 20 kHz
- (c) 2 MHz
- (d) 20 MHz.
- (c) 2 MHz use formulae ๐ = C/๐
25. Which of the following e.m. radiation has the smallest wavelength ?
- (a) Microwave
- (b) Ultra-violet
- (c) X-rays
- (d) Gamma rays
- (d) Gamma rays
26. Unit of expression ๐ป₀ฦ₀ are :
- (a) ms⁻¹
- (b) m⁻²s²
- (c) sm⁻¹
- (d) s²m²
- (b) m⁻²s²
27. Ozone layer in atmosphere is useful because it :
- (a) stops ultraviolet radiation
- (b) stops greenhouse effect
- (c) stops increase in temperature of atmosphere
- (d) absorbs polluted gases
- (a) stops ultraviolet radiation
- (a) interference
- (b) diffraction
- (c) polarisation
- (d) reflection.
- (c) polarisation
29. The frequencies of X-rays, ๐ธ-rays and ultraviolet rays are respectively a, b and c. Then :
- (a) a<b, b>C
- (b) a >b, b>c
- (c) a >b, b<c
- (d) a <b, b< c.
- (a) a<b, b>C
30. Which rays are not the portion of electromagnetic spectrum ?
- (a) X-rays
- (b) Microwaves
- (c) ๐ช-rays
- (d) Radio waves.
- (c) ๐ช-rays
31. The electromagnetic waves do not transport:
- (a) energy
- (b) charge
- (c) momentum
- (d) information.
- (b) charge
