Interference of light waves?

Question

A glass palte (n=1.53) that is .485um thick and surrounded by air is illuminated by a beam of white light normal to the plate

a.) what wavelengths (in air) within the limits of the visible spectrum (lambda=400nm to 700nm) are intensified in the reflected beam?

b.) What wavelenghts within the visible spectrum are intensified in the transmitted light?

guys!!! help me out PLEASE!!!!

Answer 1

What you need is some interferometry concepts.

The plate glass forms an etalon sort like air-surface1-medium-surface2-air. The ray or wave will bend and reflected from the surface2 and will encounter the incoming wave. If in phase then amplification will occur otherwise attenuation will take place. The phase is governed by


S=(2 pi/L)2 n l cos (A)
Whether the multiply-reflected beams are in-phase or not, depends on the wavelength (L) of the light, the angle the light travels through the etalon (A), the thickness of the etalon (l) and the refractive index of the material between the reflecting surfaces (n).
The phase difference between each succeeding reflection is given by S. See reference.
In your case
A=0

And S=(2 pi/L)2 n l
At this point note that reflected wave of the same or integer wavelength of the thickness of the glass will cause interference or cancellation with the incoming wave.
I hope it was helpful.