Question

The polarization of a helium-neon laser can change with time. The light from a laser is initially horizontally polarized; as the laser warms up, the light changes to be vertically polarized. Suppose the laser beam passes through a polarizer whose axis is 50 ∘ from horizontal.

By what percent does the light intensity transmitted through the polarizer change as the laser warms up?

Answer 1

intensityof the polarized light passing through the polarizer = I*cos²

where is the angle between polarizer and polarization of the light.

hence initial intensityof the light passing through the polarizer I₁= I*cos²50⁰

after warms up intensity of the light passing through the polarizer I₁ = I*cos²40⁰

hencepercent change of the intensity of the light =mod( ( I*cos²50⁰ - I*cos²40⁰) )*100/ I*cos²50⁰

= 100*mod(cos2*50)/cos²50⁰

= 100*mod(cos100⁰⁾/cos²50⁰

= 0.174*100/0.643²

= 42.8