Question

A thin film coating on a sunglass look reddish when observed under white illumination. The refractive index of the coating is lower than the sunglasses. Which of the following statement are TRUE about the phenomena?

A. The red light is longer in the coating than in the air.

B. The speed of the red light is slower in the coating that in the sunglasses.

C. All colour of light is either partly or completely interfered by the coating except the red light.

D. The relative phase shift between the reflected light from the air-coating interface and the coating-sunglasses is 0

Answer 1

A thin film coating on a sun glass look reddish when observed under white illumination. it is evident that all other light spectrum partly or completely diffracts from our observation , as during the sunset and sunrise all except red light of the visible spectrum are observed as red color does not deviate more , as compared to others. similarly in the coating on the sun glass,  All color of light is either partly or completely interfered by the coating except the red light.

so correct options are:

A. The red light is longer in the coating than in the air.

B. The speed of the red light is slower in the coating that in the sunglasses.

C. All color of light is either partly or completely interfered by the coating except the red light.