What is the coefficient of linear expansion of the film? Problem 35.45 Part A Wh

Question

What is the coefficient of linear expansion of the film?
Problem 35.45 Part A What is the coefficient of linear expansion of the film? (Ignore any changes in the re film due to the temperature change.) A thin uniform film of refractive index 1.750 is placed on a sheet of glass with a refractive index 1.50. At room temperature (18.4 C), this film is just thick enough for light with a wavelength 580.8 nm reflected off the top of the film to be canceled by light reflected from the top of the glass. After the glass is placed in an oven and slowly heated to 163 o C, you find that the film cancels reflected light with a wavelength 588.3 nm Express your answer using two significant figures | 17.23-10-5 | Submit My Answers Give Up Incorrect, Try Again; 5 attempts remaining Provide Feedba

Explanation / Answer

We know that,

2t = lambda

lambda = lambda0/n1

t = lambda0/2n1

t' = lambda'/2n1

from defination of linear expansion

l = l (1 + alpha. delta T)

alpha = (t' = t)/t delta T

alpha = (t'/t - 1) 1/delta T

alpha = (lambda'/lambda0 - 1)/delta T

alpha = (588.3/580.8 - 1)/(163 - 18.4) = 8.93 x 10^-5 per deg C

Hence, alpha = 8.93 x 10^-5 per deg C

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