Electromagnetic Waves And Induction(12th Grade > Physics ) Questions and answers for exam Preparation

12th Grade > Physics

ELECTROMAGNETIC WAVES AND INDUCTION MCQs

Electromagnetic Waves, Electromagnetic Induction, Waves On A String

Total Questions : 73 | Page 5 of 8 pages

Question 41. How does the speed of electromagnetic wave in vacuum depend upon the source of radiation?

Increases as we move from g-rays to radio waves
Decreases as we move from g-rays to radio waves
Is same for all of them
None of these

Discuss Question

Answer: Option C. -> Is same for all of them
:
C
The speed of EM waves in vacuum is a constant (approx.

3 \times 10^{8}

m/s).

Question 42. Which of the following are not electromagnetic waves

Cosmic rays
Gamma rays
Beta rays
X-rays

Discuss Question

Answer: Option C. -> Beta rays
:
C
Betarays are beams of fast electrons

Question 43. Radiations of intensity

0.5 W / m^{2}

are striking a metal plate. The pressure on the plate is

0.166× 10−8 N/m2
0.332× 10−8 N/m2
0.111× 10−8 N/m2
0.083× 10−8 N/m2

Discuss Question

Answer: Option A. -> 0.166× 10−8 N/m2
:
A
Intensity or power per unit area of the radiations

P = f v

\Rightarrow f = \frac{P}{v} = \frac{0.5}{3 \times 10^{8}} = 0.166 \times 10^{- 8} N / m^{2}

Question 44. The wavelength of light visible to eye is of the order of

10−2 m
10−10 m
1 m
6× 10−7 m

Discuss Question

Answer: Option D. -> 6× 10−7 m
:
D
this is the order of visible light spectrum

Question 45. Which radiation in sunlight, causes heating effect

Ultraviolet
Infrared
Visible light
All of these

Discuss Question

Answer: Option B. -> Infrared
:
B
Infrared causes heating effect

Question 46. Electromagnetic waves are transverse in nature is evident by

Polarization
Interference
Reflection
Diffraction

Discuss Question

Answer: Option A. -> Polarization
:
A
Polarization is shown by only transverse waves

Question 47. Which of the following statement is wrong

Infrared photon has more energy than the photon of visible light
Photographic plates are sensitive to ultraviolet rays
Photographic plates can be made sensitive to infrared rays
Infrared rays are invisible but can cast shadows like visible light rays

Discuss Question

Answer: Option A. -> Infrared photon has more energy than the photon of visible light
:
A
From the figure given below, you can clearly see that wave lengths of visible waves are lesser compared to wavelengths falling under infrared stage. Therefore, Infrared photon has less energy than the photon of visible light.

Which Of The Following Statement Is Wrong

Question 48. You are walking along a seashore and a mild wind is blowing. Is the motion of air a wave motion?

Yes
No
Can't say
Depends on the direction of wind

Discuss Question

Answer: Option B. -> No
:
B
When a wave propagates the particles of the medium oscillate about the mean position. In the case of a wind the particles are just flowing one side. So its not a wave motion.

Question 49. Two waves represented by

y = a s i n (ω t - k x)

and

y = a c o s (ω t - k x)

are superimposed. The resultant wave will have an amplitude

a
√2a
2a
0

Discuss Question

Answer: Option B. -> √2a
:
B
The two waves are obviously at a phase difference of

\frac{π}{2}

so the resultant amplitude

A = \sqrt{a^{2} + a^{2} + 2. a . a c o s \frac{π}{2}} = \sqrt{2} a

Question 50. Two sine waves travel in the same direction in a medium. The amplitude of each wave is A and the phase difference between the two waves is 120