You deposit a thin film of magnesium difluoride on a glass lens (n > 1.60), reducing the reflection of yellow light, at normal incidence, to a minimum. you find that the thinnest coating that accomplishes this is 106 nm thick. the index of refraction for mgf2 for yellow light (λ = 585 nm) is
a. 1.50.
b. 1.38.
c. 1.15
d. 1.00.
e. 0.707.

To solve this problem it is necessary to apply the concepts related to destructive interference.

The concept refers to an overlap of two or more waves of identical or similar frequency that, when interfering, creates a new pattern of waves of lower intensity

By definition destructive interference is given by

Where,

n=integer (1,2,3,4,5,6...etc)

t = thickness

M= Index of refrqaction

For minimum thickness to satisfy this condition n will be minimum there,

n=0

Therefore

Solving to find M,

Therefore the correct answer is B. 1.38

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force