Question

A technician places a fluid substance, with a refractive index of 1.61, between two horizontal panes of flat glass (each of which has n = 1.45). She then illuminates the assembly from above with monochromatic light (λ = 330 nm). What is the minimum thickness (in nm) that the liquid layer must have, if the light is to be strongly reflected back toward its source?

Answer 1

Answer:

the minimum thickness (in nm)  t = 102.5 nm

Explanation:

t = thickness of the film

n = index of refraction = 1.61

m = order = 1

∝ = wavelength = 330 x 10-9 m

so we have the formula

2nt = m∝

2 (1.61) t = (1) (330 x 10-9)

then...

t = 1.025 x 10-7 m

converting...

t = 102.5 nm