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

The index of refraction, n, is the ratio of the speed of light in a vacuum, c, to the speed of light in a medium, c':One consequence of this difference in speed is that when light goes from one medium to another at an angle, the propagation vector in the new medium has a different angle with respect to the normal.

The number of wavelengths in a distance d can be calculated using the following formula:

distance

And wavelength (A) in a medium having a index of refraction n will be:

An . . . . .

A = — (A0 13 wavelength 1n an, 11 IS 1ndex of refra

n

Step 2

Wavelength in the glass plate will be:

Length between source to screen is 1.8 cm, glass plate is of 25 mm thickness. Distance betWeen source and screen exc

glass plate is 1.55 cm (188-025)- 80 the number of wavelength will be-

Length between source to screen is 1-8 cm, glass plate is of 25 mm thickness- Distance betWeen source and screen excluding

glass plate is 1-55 cm (1.88—0.25). 50 the number of wavelength will be-

distance in air distance in glass

Hence, the total number of wavelengths will be -