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# Interference, Light

APPH12-BA9WDN

A circular oil slick on a calm lake has a maximum depth (in the center) of $800$ $nm$. There is a bright red fringe (due to constructive interference) in the middle where the oil slick is thickest.

How many more circular bright red ($\text{wavelength = 640 nm}$) fringes are there before the oil slick thins to a thickness of $100$ $nm$?

Note: the index of refraction of air is $1.00$, the index of refraction of oil is $1.47$, and the index of refraction of water is $1.33$.

A

0

B

1

C

2

D

more than 2