Question

A thin layer of liquid methylene iodide (n = 1.756) is sandwiched between two flat, parallel plates of glass (n = 1.50). What must be the thickness of the liquid layer if normally incident light with λ = 675 nm in air is to be strongly reflected?

Answer 1

Answer:

t = 96.1 nm

Explanation:

For strong reflection through liquid layer we know that the path difference between two reflected light rays must be integral multiple of wavelength

now we know that the path difference of two reflected light from thin liquid layer is given as

$2\mu t - \frac{\lambda}{2} = N\lambda$

here we know that

$\mu = 1.756$

t = thickness of layer

N = 0 (for minimum thickness of layer)

$\lambda = 675 nm$

now we have

$2(1.756) t = \frac{675 nm}{2}$

$t = 96.1 nm$