Q8 of 30 Page 339

A laser beam has intensity 2.5 × 1014 W m–2. Find the amplitudes of electric and magnetic fields in the beam.

Given: The intensity of laser beam =2.5 × 1014W m-2.


We have to find the amplitudes of electric and magnetic field. The


amplitude of the electric field is related to the intensity of the wave


by the relation



where


ϵ0 is the electric permittivity of free space(vacuum) and is equal to 8.85 × 10-12 C2 N-1 m-2, C is the speed of light in vacuum and is equal to 3 × 108 m s-1 and E0 is the amplitude of electric field.





.


The amplitudes of electric and magnetic fields are related as



where B0 is the amplitude of magnetic field in free space.


Thus the value of magnetic field will be


.


The electric field amplitude is and the magnetic field amplitude is .


More from this chapter

All 30 →
5

Using B = μ0 H find the ratio E0/H0 for a plane electromagnetic wave propagating through vacuum. Show that is has the dimensions of electric resistance. This ratio is a universal constant called the impedance of free space.

 6

The sunlight reaching the earth has maximum electric field of 810 V m–1. What is the maximum magnetic field in this light?

 7

The magnetic field in a plane electromagnetic wave is given by

B = (200 μT) sin [(4.0 × 1015 s–1) (t –x/c)].


Find the maximum electric field and the average energy density corresponding to the electric field.


 9

The intensity of the sunlight reaching Earth is 1380 W m−2. Assume this light to be a plane, monochromatic wave. Find the amplitudes of electric and magnetic fields in this wave.