Question

Some insect eyes have two types of cells that are sensitive to the plane of polarization of light. In a simple model, one cell type (type H) is sensitive to horizontally polarized light only, and the other cell type (type V) is sensitive to vertically polarized light only. To study the responses of these cells, researchers fix the insect in a normal, upright position so that one eye is illuminated by a light source. Then several experiments are carried out. To vary the angle as well as the intensity of polarized light, ordinary unpolarized light is passed through one polarizer with its transmission axis vertical, and then a second polarizer is placed between the first polarizer and the insect.

a)When the light leaving the second polarizer has half the intensity of the original unpolarized light, which statement is true about the two types of cells?

Only type H detects this light.

Only type V detects this light.

Both types detect this light, but type H detects more light.

Both types detect this light, but type V detects more light.

Answer 1

Suppose the intensity of the unpolarized light is . Then after passing throught the first polarizer the intensity of the light will be,

   

and the light becomes vertically polarized as the transmission axis of the first polarizer is vertical. Now according to the question the light leaving the second polarizer has also intensity,

Therefore the trasmission axis of the second polarizer is parallel with that of the first polarizer. So light leaving the second polarizer is also vertically polarized.

Hence only type V detects the light.