Light of wavelength ? strikes a pane of glass of thickness T and refractive index n, as shown in the figure below. Part of the beam is re?ected off the upper surface of the glass, and part is transmitted and then re?ected off the lower surface of the glass. Constructive interference between these two beams will occur if A) T=Wavelength/2 B) 2T=Wavelength/2 C) T = 2 Wavelength/n D) T=Wavelength/2N E) 2T=wavelength/2N Would it be the same answer for both Constructive and Destructive interference????? Solution The path difference between the two reflected waves should be same as wavelength for Constructive interference .Also, the wavelength of light when it enters the glass becomes Wavelength/n. So, 2T=Wavelength/n So, D) T=Wavelength/2N For Destructive interference, The path difference between the two reflected waves should be same as wavelength+ half wavelength. So, it Would\'nt be the same answer for both Constructive and Destructive interference. .

1. Light of wavelength ? strikes a pane of glass of thickness T and refractive index n, as shown in
the figure below. Part of the beam is re?ected off the upper surface of the glass, and part is
transmitted and then re?ected off the lower surface of the glass. Constructive interference
between these two beams will occur if
A) T=Wavelength/2
B) 2T=Wavelength/2
C) T = 2 Wavelength/n
D) T=Wavelength/2N
E) 2T=wavelength/2N
Would it be the same answer for both Constructive and Destructive interference?????
Solution
The path difference between the two reflected waves should be same as wavelength for
Constructive interference .Also, the wavelength of light when it enters the glass becomes
Wavelength/n.
So, 2T=Wavelength/n
So, D) T=Wavelength/2N
For Destructive interference, The path difference between the two reflected waves should be
same as wavelength+ half wavelength. So, it Would'nt be the same answer for both Constructive
and Destructive interference.