Go Back   Physics Help Forum > High School and Pre-University Physics Help > Light and Optics

Light and Optics Light and Optics Physics Help Forum

Reply
 
LinkBack Thread Tools Display Modes
Old Apr 13th 2014, 07:19 AM   #1
Junior Member
 
Join Date: Apr 2014
Posts: 3
Vertically polarized light from a HeNe laser passes through a linear polarizer

Q1. Vertically polarized light from a helium neon laser passes through a linear polarizer with its axis of polarization oriented 15 from the vertical axis. Assuming no absorption or reflection:
(a) What percentage of the light will be transmitted?
(b) What will be the polarization angle of the transmitted light?

A1: (a) I am reasonably certain that Malus's Law applies here:
I = I0 cos^2 θi
I = I0 cos^2 (15) =
Io 0.9330 = 93.3% Io


A1: (b) 15


Q2. In question #1, if a second polarizer is placed in the beam after the first polarizer with its axis oriented at 45 from the vertical axis:
(a) How much light is transmitted?
(b) What will be the polarization angle of the transmitted light?

A2: (a) Here is where I get messed up....Is the effect cumulative on the resulting incident light? In other words, the light passes through the first polarizer at 15 and then passes through a second polarizer oriented at 45 to the original vertical, do I add the two together (15 + 45) and use Malus's Law again for cos^2 (60)? What am I missing?
tizio is offline   Reply With Quote
Old Apr 13th 2014, 09:35 AM   #2
Junior Member
 
Join Date: Apr 2014
Posts: 3
I think I figured some of this out.

OK....I think I figured out some of this:
A2: (a) I think the formula for both polarizers is: I = Io cos^2(15) Io cos^2 (30) which ends up to be I = 0.6998 Io or 69.98% (rounded)
A2: (b) Still not quite sure how to figure out the polarization angle mathematically other than I'm pretty sure that the 45 polarizer results in quarter phase shift.
tizio is offline   Reply With Quote
Old Apr 15th 2014, 09:47 AM   #3
MBW
Senior Member
 
MBW's Avatar
 
Join Date: Apr 2008
Location: Bedford, England
Posts: 668
I am not familiar with Malus's Law,
but I think you have a flaw in the maths of A2:

The answer of A1 surely becomes the starting point for A2, thus:

I = {Io cos^2(15)} cos^2 (30)
MBW is offline   Reply With Quote
Old Apr 16th 2014, 02:46 PM   #4
Junior Member
 
Join Date: Apr 2014
Posts: 3
Yes....thank you! One Io is certainly sufficient; better than Io^2 anyway.

I = Io {cos^2(15) cos^2 (30)}
tizio is offline   Reply With Quote
Reply

  Physics Help Forum > High School and Pre-University Physics Help > Light and Optics

Tags
hene, laser, light, linear, passes, polarized, polarizer, vertically



Thread Tools
Display Modes


Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Polarized light from any suface? kelsiu Advanced Waves and Sound 1 Jul 15th 2017 09:07 AM
Can you explain how light would behave as it passes through solid opaque matter in th timemachine2 Light and Optics 0 Apr 1st 2016 10:52 AM
Object projected vertically upward-Kinetic Energy problem. Agent87 Energy and Work 3 Feb 2nd 2013 11:55 PM
Equation for linearly polarized light synclastica_86 Advanced Optics 0 Oct 20th 2009 02:05 PM
Jose can jump vertically.... Danah21 Kinematics and Dynamics 4 Feb 8th 2009 10:47 PM


Facebook Twitter Google+ RSS Feed