# Homework Help: Determine the angle of incidence

1. Dec 9, 2005

### lw11011

The index of refraction of ice is 1.79. Light is reflected from a smooth ice surface, and the reflected ray is completely polarized. Determine the angle of incidence. Answer in units of degrees.

Can anyone help me with a formula to set this one up? I'm confused on where to start.

2. Dec 10, 2005

### mezarashi

Look up the Brewster angle. Also, at this angle, the angle between the reflected and refracted rays is 90 degrees.

3. Dec 10, 2005

### daniel_i_l

$$tan(\theta) = \frac{n2}{n1}$$
This happens when the the angle between the reflected rays and refracted rays is 90 degrees, because in that case, none of the EM radiation oscillating perpendicular to the direction of the light and not paralell to the surface will be able to continue in the new direction. This is because of the fact that the EM radiation of light always oscillates on the plane perpendicular to the direction on the light (this plane can be divided into 2 cooardinites - the x_axis which is paralell to the surface and the y_axis) and never in the same direction. So when the light changes its direction by 90deg. the EM radiation perpendicular to the direction of the lights travel and not paralell to the surface(y_axis), will now have to be in the same direction as the light and so it will disappear from the light in the knew direction leaving only the light that was parallel to the surface(x_axis). So in the end, the light will be polarized with all of the EM radiation paralell to the reflective surface,

Last edited: Dec 10, 2005