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1. An electromagnetic wave in vacuum has the electric and magnetic fields E and B, which are always perpendicular to each other. The direction of propagation of the wave is along

A. E B. B C. E x B D. B x E

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2. If a source of power 4 kW produces 10^20 photons/second, the radiation belongs to a part of the spectrum called

A. microwaves B. γ-rays C. X-rays D. ultraviolet rays

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3. The electric field of an electromagnetic wave in free space is given by E = 40 cos(kz - ωt) j V/m. The magnetic field B at a point z = 0 at time t = π/(2ω) is

A. +1/3 i μT B. -1/3 i μT C. +1/3 k μT D. -1/3 k μT

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4. A plane electromagnetic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time, E = 6.3 j V/m. The corresponding B at that point is

A. 2.1 x 10^-8 k T B. 2.1 x 10^-8 i T C. 2.1 x 10^-8 j T D. 2.1 x 10^-8 k T

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5. The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is

A. 1:1 B. c:1 C. 1:c D. c^2:1

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6. The electric field of an electromagnetic wave in free space is given by E = 40 cos(kz - ωt) j V/m. The frequency of the wave is

A. 6.0 x 10^6 Hz B. 12.0 x 10^6 Hz C. 6.0 x 10^7 Hz D. 12.0 x 10^7 Hz

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7. The electric field of an electromagnetic wave in free space is given by E = 40 cos(kz - ωt) j V/m. The wavelength of the wave is

A. 7.5 m B. 15 m C. 30 m D. 60 m

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8. The electric field of an electromagnetic wave in free space is given by E = 40 cos(kz - ωt) j V/m. The wave propagates along

A. x-direction B. y-direction C. z-direction D. -z-direction

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9. The electric field of an electromagnetic wave in free space is given by E = 40 cos(kz - ωt) j V/m. The magnetic field B is given by

A. B = (1/3) cos(kz - ωt) i μT B. B = (1/3) cos(kz - ωt) j μT C. B = (1/3) cos(kz - ωt) k μT D. B = (1/3) cos(kz - ωt) -i μT

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10. The intensity of an electromagnetic wave is proportional to

A. E^2 B. B^2 C. EB D. E/B

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11. Which electromagnetic wave has the highest frequency?

A. radio waves B. microwaves C. infrared waves D. gamma rays

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12. Electromagnetic waves transport

A. energy only B. momentum only C. energy and momentum D. neither energy nor momentum

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13. Which of the following properties is not common to all electromagnetic waves?

A. reflection B. diffraction C. polarization D. none of these

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14. The velocity of electromagnetic waves in a medium depends on

A. permeability only B. permittivity only C. both permeability and permittivity D. neither permeability nor permittivity

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15. Which electromagnetic wave is used in medical imaging?

A. radio waves B. X-rays C. gamma rays D. infrared waves

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16. The energy of an electromagnetic wave is proportional to

A. amplitude B. frequency C. wavelength D. velocity

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17. In electromagnetic waves, the phase difference between the electric and magnetic fields is

A. 0 B. π/2 C. π D. none of these

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18. Which electromagnetic wave is used in remote sensing?

A. infrared B. microwaves C. ultraviolet D. gamma rays

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19. Which wave has the shortest wavelength?

A. radio waves B. microwaves C. ultraviolet rays D. gamma rays

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20. The speed of electromagnetic waves in free space is approximately

A. 3 x 10^8 m/s B. 3 x 10^6 m/s C. 3 x 10^10 m/s D. 3 x 10^5 m/s