In the figure below, light is incident perpendicularly on a thin layer of materi

Question

In the figure below, light is incident perpendicularly on a thin layer of material 2 that lies between (thicker) materials 1 and 3. (The rays are tilted only for clarity.) Part of the light ends up in material 3 as ray r3 (the light does not reflect inside material 2) and r4 (the light reflects twice inside material 2). The waves of r3 and r4 interfere, and here we consider the type of interference to be either maximum (max) or minimum (min). For this situation, n1 = 1.30, n2 = 1.52, n3 = 1.90, and L = 260 nm. Give the wavelength that is in the visible range. (State the visible wavelength when rays r3 and r4 undergo maximum constructive interference.)

Explanation / Answer

apply the formula for minimum thickness at tmin = L/4n

where L is wavelegnth

and n is refractive index

so

for n1 = 1.3 and L = 260 nm

tmin = 260 e-9 /(4*1.3)

tmin = 50 nm

---------------------------------

for n1 = 1.52 and L = 260 nm

tmin = 260 e-9/(4*1.52)

tmin = 42.76 nm

---------------------------------

for n1 = 1.9 and L = 260 nm

tmin = 260 e-9/(4*1.9)

tmin = 34.21 nm

---------------------------------

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects