• Support PF! Buy your school textbooks, materials and every day products Here!

Light Polarization

  • Thread starter Dart82
  • Start date
  • #1
57
0

Homework Statement

Light that is polarized along the vertical direction is incident on a sheet of polarizing material. Only 66% of the intensity of the light passes through the sheet and strikes a second sheet of polarizing material. No light passes through the second sheet. What angle does the transmission axis of the second sheet make with the vertical?
[URL=http://img87.imageshack.us/my.php?image=lightintensityds5.png][PLAIN]http://img87.imageshack.us/img87/2071/lightintensityds5.th.png[/URL][/PLAIN]



Homework Equations


If light intensity = S, then the light passing through a polarizer = (1/2)S
Malus Law: Averge intensity of light leaving the analyzer = (.5*S)cos^2(theta)



The Attempt at a Solution


At 90 degress from the vertical, the polarizer would block all light from passing through. however the problem states that 66% of the light passes through the polarizer. I think that an angle that is 33% of 90 degrees would allow 66% of the light to pass through the polarizer. if i am correct in thinking that a polarizer must be at 90 degrees to block light, then the analyzer must be at a 90 with the polarizer which is at a 30 degree angle with respect to the vertical. 30 degrees + 90 degrees = 120 degrees from the vertical.
 

Answers and Replies

  • #2
70
0
You are right that the second sheet is at 90 degrees to the first. However your angle for the first sheet is wrong. You need to use Malus to find this angle.
However you have not quoted Malus law correctly.

Transmitted intensity = [tex]s*cos^2(/the)[/tex]

(There should not be a half in front of this.)

We do not know initial intensity but we know it is cut down by 66% after the first sheet. Therefore the transmitted intensity = 0.66*s.

Put this into the Malus law and solve for theta.
 
  • #3
57
0
the more i thought about it the more confused i seemed to get. thanks..i finally got it
 

Related Threads on Light Polarization

  • Last Post
Replies
7
Views
435
  • Last Post
Replies
3
Views
5K
Replies
2
Views
6K
  • Last Post
Replies
7
Views
761
  • Last Post
Replies
3
Views
687
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
7
Views
4K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
5
Views
1K
  • Last Post
Replies
3
Views
1K
Top