Advertisements
Advertisements
Question
What is antireflection coating? What should be the refractive index and minimum thickness of the coating?
Solution
When the light enters the optical instrument at the glass air interface, around 4% of light that too at single reflection is lost by reflection which is highly undesirable. In order to reduce the reflection loss, a transparent film of proper thickness is deposited on the surface. This film is known as antireflective coating.
Popular material used is MgF2 because of its refractive index is 1.38.
The minimum thickness of coating is given by: -
2nt = mλ
n = refractive index of film
t = thickness of film
m = 1, 2, 3, …
λ = light wavelength in vacuum (air)
APPEARS IN
RELATED QUESTIONS
Obtain the condition for maxima and minima of the light reflected from a thin transparent film of uniform thickness. Why is the visibility of the fringe much higher in the reflected system than in the transmitted system.
What is meant by thin film? Comment on the colours in thin film in sunlight.
Derive the conditions of maxima and minima due to interference of light transmitted from thin film of uniform thickness.
Derive the conditions of maxima and minima due to interference of light reflected from thin film of uniform thickness.
