Question

A sheet of glass is coated with a 501-nm-thick layer of oil (n = 1.42).

1.For what visible wavelengths of light do the reflected waves interfere constructively?

2.For what visible wavelengths of light do the reflected waves interfere destructively?

3.What is the color of reflected light?

	Red
	Yellow
	Orange
	Green-blue

4.What is the color of the most part of transmitted light?

	Yellowish green
	Blue
	Orange
	Red

Answer 1

for construvtive interference path difference = 1,2 times wavelength

path difference = 2*t / N

for 1*lambda

1*wavelength = 2*501/1.42 = 705.633 nm

for 2 lambda

2*lambda = 2*501/1.42

lambda = 352.81 nm (not visible)

so wavelength for constructive interference = 705.633 nm

b) for destructive interference path difference = 1/2 or 3/2 wavelengths

for 1/2 lambda

1/2*lambda = 2*501/1.42

lambda = 1411.267 nm ( not visible)

for 3/2 lambda

3/2*lambda = 2*501/1.42

lambda = 470.422 nm

c) color of reflected light is red

d) color of most part of transmitted light is blue