# Reflection dependence from wavelenght

## Homework Statement

Hi guys, I have this exercise and I m confused.
Incident (white light) light ray is perpendicular to glass surface , glass plate is 0,4microm thick. Which wavelengths in reflected ray becomes more intense?

## The Attempt at a Solution

So i know that light is refracted on the surface of 2 different mediums, different wavelengths are refracted in different angles.
But i do not know nothing about wavelength and/or intensity dependence from reflection. And its seems weird that intensity of some wavelengths increases after reflection.

Could someone,please, help?
Maybe some tips about which physical phenomenon I should study?

ehild
Homework Helper

## Homework Statement

Hi guys, I have this exercise and I m confused.
Incident (white light) light ray is perpendicular to glass surface , glass plate is 0,4microm thick. Which wavelengths in reflected ray becomes more intense?

## The Attempt at a Solution

So i know that light is refracted on the surface of 2 different mediums, different wavelengths are refracted in different angles.
But i do not know nothing about wavelength and/or intensity dependence from reflection. And its seems weird that intensity of some wavelengths increases after reflection.

Could someone,please, help?
Maybe some tips about which physical phenomenon I should study?
Think of interference. For which wavelength is constructive interference in the reflected light?

• prehisto
Think of interference. For which wavelength is constructive interference in the reflected light?

Thank you for your reply
Ok, I think I go it.
First I calculate the angle of light ray inside the glass from Snell's law.
Second I use Thin films equation for constructive interference and calculate the wavelengths by altering m in the formula.
Correct?

ehild
Homework Helper
Thank you for your reply
Ok, I think I go it.
First I calculate the angle of light ray inside the glass from Snell's law.
Second I use Thin films equation for constructive interference and calculate the wavelengths by altering m in the formula.
Correct?
No need to calculate the angle, as the incidence is perpendicular, that is, the angle of incidence is 0 degree. The refracted ray does not change direction.
The second plan is correct, find the condition for constructive interference for reflected light and select the wavelength by altering m.

No need to calculate the angle, as the incidence is perpendicular, that is, the angle of incidence is 0 degree. The refracted ray does not change direction.
The second plan is correct, find the condition for constructive interference for reflected light and select the wavelength by altering m.

OK, thank you again for help!