What is the smallest thickness of a coating of magnesium fluoride (n = 1.38) applied to glass (n = 1.50) that gives minimum reflection for 600 nm light?
A) 600 nm
B) 300 nm
C) 435 nm
D) 109 nm
E) 100 nm

Question

Quizplus · Accepted Answer

For a coating to give a minimum reflection, the thickness should be equal to λ/4n.
λ = 600 nm
n (glass) = 1.50
n (MgF2) = 1.38

Thus, the thickness of the coating of MgF2:
t = λ/4n
t = (600 nm)/(4*1.38)
t = 109 nm

Therefore, the correct answer is D) 109 nm.

What Is the Smallest Thickness of a Coating of Magnesium