Physics

We want to rotate the direction of polarization of a beam of polarized light through 90 degrees by sending the beam through one or more polarizing sheets.(a) What is the mini-mum number of sheets required? (b) What is the minimum number of sheets required if the transmitted intensity is to be more than 60% of the original intensity?

  1. 👍 0
  2. 👎 0
  3. 👁 531
asked by Brian
  1. Since when can polarizing sheets rotate a linearly polarized light beam?

    1. 👍 0
    2. 👎 0
  2. I don't really know. I did ln(1/100)=-4.605 and ln(cos(90)^2)=-1.605 and 4.605/1.605=2.869. The answer for part (a) should be 2 but 2.869 is closer to 3 so am I doing anything wrong?

    1. 👍 0
    2. 👎 0
    posted by Brian
  3. (a)If we place one sheet with its polarization direction 90⁰ to the polarized light then the transmitted intensity will be zero (since I=I₀•cos²α = I₀•cos²90⁰=0).
    If we use 2 sheets, the 1st sheet rotates by angle α (0< α<90⁰) and the 2nd sheet rotate by the angle (90⁰-α)
    I=I₀•cos²α•cos²(90⁰-α)= I₀•cos²α•sin²α.
    Thus, we need two sheets.
    (b) I=I₀•cos²ⁿ(90⁰/n)
    n=2 I₂=I₀•cos⁴(90⁰/2)=0.25•I₀
    n=3 I₃=I₀•cos⁶(90⁰/3)=0.422•I₀
    n=4 I₄=I₀•cos⁸(90⁰/4)=0.53•I₀
    n=5 I₅=I₀•cos¹⁰(90⁰/5)=0.6054•I₀
    I ո ≥0.6•I₀
    Thus, the minimum value n=5 sheets.

    1. 👍 2
    2. 👎 0
    posted by Elena
  4. I still don't understand part (a). I know that cos^2(90)=0 but how did you get to the answer of 2 sheets?

    1. 👍 0
    2. 👎 0
    posted by Brian
  5. 2 because....that's the minimum no. of angles of that can ad up to 90

    1. 👍 0
    2. 👎 0
    posted by Rajnit

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics

    A beam of partially polarized light can be considered to be a mixture of polarized and unpolarized light. Suppose a beam of partially polarized light is sent through a polarizing filter. The polarization direction of the filter

    asked by Po on November 18, 2016
  2. Physics

    We want to rotate the direction of polarization of a beam of polarized light through 90 degrees by sending the beam through one or more polarizing sheets. (a) What is the mini-mum number of sheets required? (b) What is the minimum

    asked by Brian on December 20, 2012
  3. Physics

    A beam of polarized light with an average intensity of 17.1 W/m2 is sent through a polarizer. The transmission axis makes an angle of 27° with respect to the direction of polarization. Determine the rms value of the electric

    asked by Elizabeth on March 26, 2013
  4. physics

    Is saying light is electrically polarized , saying it is an electric dipole? Your question can be answered using either wave or particle models of light. In the wave model, polarization is related to the direction of the

    asked by laura on June 11, 2007
  5. Physics

    Is it impossible to polarize a longitudinal wave? Explain. Longitudinal waves are polarized in the direction of propagation, they vibrate in that direction. But in the usual sense of polarization (Electric component of light), it

    asked by Caleb on April 18, 2007
  6. chemisrty

    Will 1,1,2, trichloro ethane rotate polarized light if it is cooled to low temperature and trapped in its lowest energy position? Yes, under all circumstances. Yes, but only if it is chiral. No, it will never rotate light. No,

    asked by Anonymous on June 1, 2013
  7. physics

    An analyzer is rotated about an incident ray. The intensity of light is found to increase and decrease, but it does not become zero at any point. The incident light is: a.partially polarized b.plane-polarized c.polarized in two

    asked by HELP on December 16, 2009
  8. Physics

    Beam supported by a rope that can rotate about a hinge. The beam is supported by a rope attached 1.00 meter from the end of the beam. The beam has a mass of 10.0 kg and is 6.00 meters long. The rope makes a 60degree angle. What is

    asked by Fred on November 17, 2015
  9. physics

    The sugar concentration in a solution (e.g., in a urine specimen) can be measured conveniently by using the optical activity of sugar and other asymmetric molecules. In general, an optically active molecule, like sugar, will

    asked by Jason on October 21, 2014
  10. much needed help...

    The sugar concentration in a solution (e.g., in a urine specimen) can be measured conveniently by using the optical activity of sugar and other asymmetric molecules. In general, an optically active molecule, like sugar, will

    asked by jason on October 22, 2014

More Similar Questions