Transverse waves, as they travel forward, vibrate in certain directions, up and down and from side to side as shown.

Light can be polarized in any direction except forwards and backwards – by which we mean the electric field can vibrate up or down or any angle in between, as illustrated here. Polarization occurs when the electeic field is forced to oscillate in one direction only.

Light passing throughemerges vertically polarized. Then no light can pass throughn general if polarized light of Intensityin incident on a polarizing filter oriented at an anglethen the intensity of the emerging light is given by