53.8k views
5 votes
Three perfectly polarizing sheets are spaced 2?cm {\rm cm} apart and in parallel planes. The transmission axis of the second sheet is 28 ? \deg relative to the first one. The transmission axis of the third sheet is 90 ? ^\circ relative to the first one. Unpolarized light impinges on the first polarizing sheet.

What percent of this light is transmitted out through the third polarizer?

User DarkLegend
by
8.6k points

1 Answer

2 votes

Answer:

I₃/Io % = 0.8.59

Step-by-step explanation:

A polarizer is a complaint sheet for light in the polarization direction and blocks the perpendicular one. When we use two polarizers the transmission between them is described by Malus's law

I = I₀ cos² θ

Let's apply the previous exposures in our case, the light is indicatively not polarized, so the first polarized lets half of the light pass

I₁ = ½ I₀

The light transmitted by the second polarizer

I₂ = I₁ cos² θ

I₂ = (½ I₀) cos2 28

The transmission by the polarizing third is

I₃ = I₂ cos² θ₃

The angle of the third polarizer with respect to the second is

θ₃ = 90-28

θ₃ = 62º

I₃ = (½ I₀ cos² 28 cos² 62)

Let's calculate

I₃ = Io ½ 0.7796 0.2204

I₃ = Io 0.0859

I₃/Io= 0.0859 100

I₃/Io % = 0.8.59

User Lyokolux
by
8.7k points