Adv Physics
Thin Films
λ’ = λ / n
Name _________________________________________
Date_____________________________ Per ________
2nt = ( m+ ½ ) λ
2nt = ( m ) λ
1) A beam of light (λ = 534 nm) passes through two parallel and very close glass plates ( n= 1.52 ).
What is the minimum thickness of the air (n = 1.0003) between the glass plates that would make
the transmitted beam bright? Draw a sketch of the glass plates.
2) A beam of light of 540.6 nm light is illuminating two close glass plates with a parallel orientation.
As they are pulled apart the beam goes dark to bright to dark. How far were these plates moved?
3) A soapy film of water in air (a soap bubble) has an index n = 1.358 and a thickness of 6.50 E -4
mm. What wavelengths of visible light will be strongly reflected if the light hits normally?
4) What is the minimum thickness of a soap film (n= 1.360) that will transmit with constructive
interference a wavelength of 589.6 nm?
5) A film (t= 550 nm) of oil (n= 1.468) on top of a sheet of water is illuminated from above. What
visible wavelengths will be strongly reflected?
6) Find the minimum thickness anti reflection coating (a dielectric material of n= 1.334)
on the surface of a glass camera lens ( n= 1.565 ) to give a minimum reflection at 550 nm.