[ف.نووي]

In a Newton’s rings apparatus, find the phase difference (in radians) when an air wedge of 500 nm thickness is illuminated with red light ( = 640 nm).
a. 13 b. 11 c. 9
d. 7 e. 3
solution:

Δ=2t+λ/2=2×500nm+640nm/2 =13