(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Calculate the minimum thickness of a layer of manesium flouride(n=1.38) on flint glass (n=1.66) in a lens system, if light wavelength 5.50x10^2 nm in air undergoes destructive interference.

Given:

n1=1.38

n2=1.66

λ1=5.5*10^2 nm

2. Relevant equations

Δx=L(λ/2t)

n2/n1 = λ1/λ2

3. The attempt at a solution

Destructive interference is at λ/4, 3λ/4, 5λ/4 ....

So the λ in flint flass is λ2=(n1*λ)/n2

= 4.57 * 10^-7

Therefore the shortest thicknss should be λ/4

4.57*10^-7/4

1.14*10^-7

The answer however is wrong the answer is suppose to be 199 nm.

Can someone please help! Thanku

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Calculate Interference in thin films

**Physics Forums | Science Articles, Homework Help, Discussion**