Question

Suppose that a beachgoer uses two lenses from a pair of disassembled polarized sunglasses and places one on top of the other. What would he observe if he rotates one lens 90° with respect to the normal position of the other lens and looks through them directly at the sun overhead?

Group of answer choices

Light with an intensity that is the same of what it would be with one lens

Light with an intensity reduced to about 50% of what it would be with one lens

Complete darkness, since no light would be transmitted

Light with an intensity reduced to about 25% of what it would be with one lens

Answer 1

When the lighy is passed through first polarizing lens the light gets polarized in specific direction. We suppose yhe lens is verical polarizer. Then all the horizontal components of light are absorbed by the glass and only vertical component is transmitted. Thus the emerging ray from first lens would be vertically polarized.

If these vertically polarized waves are then passed through another pair of lenses, the final polarization would be the same as the polarization of the second lens.

The intensity of polarized light is given by

I = I0 ( cos(θ) )2
where
I is the intensity of the incoming light
I0 is the intensity of the resultant light
θ is the angle between the the polarization of first lens and the polarization of second lens.

Thus if the second polarizing lens is horizontal i.e. making 900 angle with the first lens then cos(900)=0 thus intensity of light through second lens would be zero. No light is transmitted.

Thus answer is Complete darkness, since no light would be transmitted.