Question

A He-Ne laser produces light of 633 nm wavelength, 1.5 mW power, with a cylindrical beam of 0.64 mm in diameter.

Answer 1

Answer:

a. 4662.7W/m^2

b. the damage threshold is 100W/m^2 , therefore the laser is not safe to view if the intensity is 4662.7W/m^2

c. Bmax=6.24*10^-6T

d average intensity=0.01W/cm^2

Explanation:

A He-Ne laser produces light of 633 nm wavelength, 1.5 mW power, with a cylindrical beam of 0.64 mm in diameter.

(a) What is the intensity of this laser beam?

(b) The damage threshold of the retina is 100 W/m2 . Is this laser safe to view head-on?

(c) What are the maximum values of the electric and magnetic fields?

(d) What is the average energy density in the laser beam?

firstly, we get the relation between power and intensity to be

P=IA

1.5*10^-3=I*$\pi *(0.32*10^{-3} )^2$

I=4662.74W/m^2

b. the damage threshold is 100W/m^2 , therefore the laser is not safe to view if the intensity is 4662.7W/m^2

c.e=$\sqrt{ \frac{2I}{Ec} }$

$\sqrt{ \frac{2*4662}{8.85*10^-12*3*10^8} }$

e=(3512391.71)^0.5

e=1874.13W/m^2

maximum values of electric and magnetic fields

Bmax=e/c

c=speed of light 3*10^8 m/s^2

Bmax=1874/3*10^8

Bmax=6.24*10^-6T

d.intensity=average intensity(1/10^2)^2

intensity=0.01W/cm^2