Advertisements
Advertisements
Question
An unpolarised light of intensity 32 Wm-2 passes through three Polaroids such that the axes of the first and the last Polaroids are at 90°. What is the angle between the axes of the first and middle Polaroids so that the emerging light has an intensity of only 3 Wm-2?
Advertisements
Solution
Given: I = 3 Wm-2, I0 = 32Wm-2, θ = ?
∴ `"I"_circ = "KA"^2`
I = K AR2
I = `("K A"^2)/2 cos^2 theta sin^2 theta`
`"A"_"R" = "A"/sqrt2 cos theta sin theta`
`"I" prop "AR"^2`
I = `"I"_0/2 4/4 cos^2theta sin^2theta`
I = `"I"_0/8 (2 cos theta sin theta)^2`
I = `"I"_0/8 (sin 2 theta)^2`
`3 = 32/8 (sin 2 theta)^2`
`(sin 2 theta)^2 = 3/4`
`(sin 2 theta) = sqrt3/2`
2θ = 60°
θ = 30°
APPEARS IN
RELATED QUESTIONS
What is a Polaroid?
Draw a neat labelled diagram showing the plane of vibration and plane of polarisation for polarised light.
If the critical angle of a medium is sin-1(3/5), find the polarising angle.
Show, using a simple polaroid, that light waves are transverse in nature. Intensity of light coming out of a polaroid does not change irrespective of the orientation of the pass axis of the polaroid. Explain why.
Two polaroids P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity I0 is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle of 60° with that of P1. Determine the intensity of light transmitted through P1, P2 and P3.
Show using a proper diagram how unpolarised light can be linearly polarised by reflection from a transparent glass surface.
With the help of an experiment, state how will you identify whether a given beam of light is polarised or unpolarized?
Unpolarised light is incident on a polaroid. How would the intensity of transmitted light change when the polaroid is rotated?
A ray of light is incident on a transparent medium at a polarizing angle. What is the angle between the reflected ray and the refracted ray?
Explain how an unpolarised light gets polarised when incident on the interface separating the two transparent media.
Greenlight is an incident at the polarising angle on a certain transparent medium. The angle of refraction is 30°.
Find
(i) polarising angle, and
(ii) refractive index of the medium.
The transverse nature of light is shown in ______.
What is polarisation?
What is partially polarised light?
Mention the types of optically active crystals with example.
Which of the following phenomena is not common to sound and light waves?
Figure shown a two slit arrangement with a source which emits unpolarised light. P is a polariser with axis whose direction is not given. If I0 is the intensity of the principal maxima when no polariser is present, calculate in the present case, the intensity of the principal maxima as well as of the first minima.
A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just 10% of the original intensity. Assuming that the polarizer - analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero, is ______.
