Class 12 Physics Wave Optics Polarization by reflection and refraction

Polarization by reflection and refraction

• When an unpolarized beam of light falls on boundary, reflected wave and refracted wave are partially polarized.
• An incident wave is an unpolarized light .Some of the rays will get reflected and some gets refracted.
• Most of the light waves that reflected were polarized waves, which were parallel to the plane.
• Most of the rays along the refracted ray were unpolarized waves with one or two polarized components.
• Refracted Ray à More unpolarized and Reflected rayà more polarized.
• If the angle of incidence varies more and more unpolarized light was able to pass through the surface.
• At one particular value of angle of incidence there was maximumpolarization in the reflected ray.
• Above and below the value of angle of incidence, both reflected and refracted rays were partially polarized.

Brewster’s law:- Brewster’s law states that at any particular angle of incidence, reflected ray is completely polarized; and the angle between reflected and refracted ray is 900.

• At i = iB; where iB = Brewster’s angle of incidence.
• From Snell’s law :- (sin i/sin r)= μ
• => sin iB /(sin (π/2 -iB))
• =>(sin iB /cos iB)=μ
• tan iB = μ

Problem:-

What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5.)

Refractive index of glass,μ=1.5

Brewster angle = θ

Brewster angle is related to refractive index as:

tan θ =μ

θ =tan-1(1.5) =56.310

Therefore, the Brewster angle for air to glass transition is 56.31°.

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