ELECTROMAGNETIC WAVES

11 )

Electric field in an electromagnetic wave is given by E = 50 sin ω [t – (x/c)]N C^–1. Intensity of this wave is _______Wm^–2

Select correct option from the following options.

(A) 50 (B) 1.1 × 10⁸

View Solution

Answer :

E = 50 sin ω [t – (x/c)]

Here E_o = 50

we know E_o = √(2I / E_oC)

where I = intensity, hence

E_o² ∙ E_o ∙ C = 2I

I = [(E_o² ∙ E_o ∙ C) / 2]

= [{(50)² × 8.85 × 10^–12 × 3 × 10⁸} / 2]

= 3.31 W/m²

12 )

The amplitude of the electric field in a parallel beam of light of intensity 2.0 Wm^–2 is ________

Select correct option from the following options.

(A) 38.8 NC^–1 (B)19.4 NC^–1

View Solution

Answer :

E_o = √(2I / E_oC)

As I = intensity = 2 W/m²

E_o = 8.85 × 10^–12

C = 3 × 10⁸ m/s

∴ E_o = √[(2 × 2) / (8.85 × 10^–12 × 3 × 10⁸)]

= √(1506.59)

= 38.81 N/C

13 )

Speed of electromagnetic wave is the same

for all wavelengths

in all media

for all intensities

for all frequencies

View Solution

Answer :

Speed of electromagnetic wave is the same for all intensities.

14 )

The maximum electric field in a plane electromagnetic wave is 900NC^–1. The wave is going in the x direction and the electric field is in the y direction. The maximum magnetic field in the wave is ________ T

Select correct option from the following options.

(A) 3 × 10^–8 (B) 3 × 10^–6

View Solution

Answer :

given E_o = 900N/C

Let maximum value of magnetic field be B_o

As B_o = (E_o / C)

hence B_o = [900 / (3 × 10⁸)]

= 300 × 10^–8

= 3 × 10^–6 T

15 )

Electromagnetic waves are produced by

a static charge

a moving charge

an accelerating charge

charge less particles

View Solution

Answer :

Electromagnetic waves are produced by accelerating charge.

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