A glass plate 2.95 thick, with an index of refraction of 1.60, is placed between a point source of light with wavelength 600 nmnm (in vacuum) and a screen. The distance from source to screen is 1.25 cm. How many wavelengths are there between the source and the screen?

Explanation:

Given;

Thickness of the glass plate,

refractive index of the glass plate,

wavelength of light source in vacuum,

distance between the source and the screen,

Distance travelled by the light from source to screen in vacuum:

So the no. of wavelengths in the vacuum:

 .......................(1)

Now we find the wavelength of the light wave in the glass:

where:

wavelength of light in the medium of glass.

Now the no. of wavelengths in the glass:

............................(2)

From (1) & (2):