Polarisation Contents: EM Waves Polarisation angle Polaroid filters Brewster’s angle

Concept of polarization: Demo - Spring

Plane Polarized light: I o – incident intensity (W/m 2 ) Demo two polarizers

More than one polarizer: I = I o cos 2  I o – incident intensity of polarized light I – transmitted intensity (W/m 2 )  – angle twixt polarizer and incident angle of polarization Demo two polarizers IoIo ½I o ( ½ I o )cos 2 

Two polarizers are at an angle of 37 o with each other. If there is a 235 W/m 2 beam of light incident on the first filter, what is the intensity between the filters, and after the second? I = I o cos 2  After the first polarizer, we have half the intensity: I = 235/2 = W/m 2 and then that polarized light hits the second filter at an angle of 37 o : I = (117.5 W/m 2 ) cos 2 (37 o ) = = 75 W/m 2

Brewster’s angle: non-metallic surface reflected light polarized parallel to surface. In general n 2 = tan  n 1 For air (n 1 = 1.00) to something: n = tan  demo – small polarizers

Polarization 11 | 22 TOC

I = ?, I o = 120. W/m 2,  = 21.0 o I = W/m W/m 2 W 120. W/m 2 of vertically polarized light goes through a filter that makes an angle of 21.0 o with the vertical. What is the transmitted intensity? I = I o cos 2 

I = 80.0 W/m 2, I o = 120. W/m 2,  = ?  = o 35.3 o W 120. W/m 2 of vertically polarized light goes through a filter that makes some angle with the vertical such that only 80.0 W/m 2 are transmitted. What angle does the filter make with the vertical? I = I o cos 2 

After the first filter, we are down to 250 W/m 2, Then we use the formula I = I o cos 2  = (250 W/m 2 )cos(68.0 o ) 2 = W/m W/m 2 W 500. W/m 2 of UNpolarized light goes through a vertically polarized filter, and then through one the makes an angle of 68.0 o with the vertical. What is the transmitted intensity? I = I o cos 2 

n = 1.33,  = ?  = o 53.1 o W What is Brewster’s angle from air to water? (n = 1.33) n = tan 

n = ?,  = 67.5 n = W What is the index of refraction of a substance that has a Brewster’s angle of o ? n = tan 

Demos Optical activity Light Show Stress and Activity Birefringence