A ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness ' t ' and refractive index ' n ' is introduced in i

Question

A ray of light from a monochromatic point source of light is incident at a point on the screen. If a thin mica film of thickness ' t ' and refractive index ' n ' is introduced in its path, then the optical path

TestHub · Accepted Answer

The optical path of a light ray traveling a distance $t$ in a medium of refractive index $n$ is $n t$ .

Before the introduction of the mica film, the light ray traveled the same distance $t$ in air, so the optical path was $t$ .

The change in the optical path is the difference between the new optical path and the old optical path.

Change in optical path $= n t - t = (n - 1) t$ .

Since $n > 1$ , the optical path is increased by $(n - 1) t$ .

Answer: is increased by $(n - 1) t$ .

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