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#### Electromagnetic waves One Mark Questions with Answer

12th Standard EM

Reg.No. :
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Physics

Time : 00:45:00 Hrs
Total Marks : 25
25 x 1 = 25
1. Which of the following electromagnetic radiation is used for viewing objects through fog

(a)

microwave

(b)

gamma rays

(c)

X- rays

(d)

infrared

2. Let E = Eo sin[106 x -ωt] be the electric field of plane electromagnetic wave, the value of ω is

(a)

(b)

(c)

(d)

3. The electric and magnetic fields of an electromagnetic wave are

(a)

in phase and perpendicular to each other

(b)

out of phase and not perpendicular to each other

(c)

in phase and not perpendicular to each other

(d)

out of phase and perpendicular to each other

4. The wavelength range of ultra violet radiation is

(a)

6x10-10 to 4x10-7m

(b)

4x10-7 to 7x10-7m

(c)

6x10-10 to 4x10-10m

(d)

7x10-7 to 4x10-9m

5. The phase and orientation of the magnetic vector associated with electromagnetic oscillations differ respectively from those of the corresponding electric vectors by

(a)

zero, zero

(b)

$\frac{\pi}{2}$,$\frac{\pi}{2}$

(c)

0, $\frac{\pi}{2}$

(d)

0,$\frac{\pi}{2}$

6. In vacuum speed of light depends upon

(a)

colour

(b)

wavelength

(c)

frequency

(d)

none of the above

7. Short wave bands are upto frequencies

(a)

54 KHz

(b)

5.4 MHz

(c)

54 MHz

(d)

54 GHz

8. The correct definition of spectrum is

(a)

band of colours

(b)

band of white light

(c)

band of frequencies

(d)

band of amplitudes

9. The spectra used for making dyes is

(a)

line spectra

(b)

continuous absorption spectra

(c)

fraunhofer spectra

(d)

band absorption spectra

10. Band spectra are obtained from _________.

(a)

atoms

(b)

molecules

(c)

solids

(d)

semisolids

11. Calcium or Barium salts in bunsen flame, CO2, N2 molecule, NH3 gas in a discharge tube gives_______.

(a)

line emission spectra

(b)

continuous emission spectra

(c)

line absorption spectra

(d)

band spectra

12. The value of $\frac { 1 }{ \sqrt { { \mu }_{ 0 }{ \varepsilon }_{ 0 } } }$ _________

(a)

3 x 10-8 m/s

(b)

2.25 x 108 m/s

(c)

3 x 108 m/s

(d)

2.25 x 108 m/s

13. The rays used in weather forecasting is ___________.

(a)

I-R rays

(b)

U-V rays

(c)

X - rays

(d)

μ-Waves

14. Electromagnetic waves are __________.

(a)

longitudinal waves

(b)

mechanical waves

(c)

Transverse waves

(d)

Straight waves

15. Angle between the electric and magnetic component of EM wave is

(a)

0

(b)

π/4

(c)

π/2

(d)

π

16. In E.M. waves, the variations in electric and magnetic fields are at an angle of________.

(a)

(b)

60°

(c)

90°

(d)

270°

17. In an electromagnetic wave, the electric and magnetic fields are at an angle ___________ to the direction of propagation.

(a)

270°

(b)

90°

(c)

180°

(d)

67°

18. The wavelength range of x-rays is _________ (m).

(a)

10-4 to 10-2

(b)

10-14 to 10-9

(c)

10-10 to 3 X 10-8

(d)

10-3 to 10-5

19. Vacuum tubes produces ________

(a)

Visible light

(b)

RF waves

(c)

UV rays

(d)

Microwaves

20. Microwaves ovens are the domestic application of ________ wave.

(a)

UV

(b)

visible

(c)

(d)

micro

21. ________ lamps are used in physiotherapy.

(a)

IR

(b)

UV

(c)

visible

(d)

૪-rays

22. ________ radiations are used to study atomic structure.

(a)

UV

(b)

IR

(c)

X-rays

(d)

Gamma

23. ______ radiations are used in destroying bacteria.

(a)

UV

(b)

IR

(c)

X-ray

(d)

Gamma rays

24. _________ emission spectrum is used to identify the gas used.

(a)

Continuous

(b)

Line

(c)

Band

(d)

Solid

25. The dark lines in the solar spectrum are called _______ lines.

(a)

Fresnel

(b)

Newton

(c)

Compton

(d)

Fraunhofer