Question:
Two polaroids $A$ and $B$ are placed with their polaroid axes $30^{\circ}$ to each other as shown in the figure. A plane polarized light passes through the polaroid $A$ and after passing through it, intensity of light becomes $I_0$.What is the intensity of finally transmitted light after passing through the polaroid $B$ ?
Two polaroids $A$ and $B$ are placed with their polaroid axes $30^{\circ}$ to each other as shown in the figure. A plane polarized light passes through the polaroid $A$ and after passing through it, intensity of light becomes $I_0$.What is the intensity of finally transmitted light after passing through the polaroid $B$ ?
Updated On: Jun 20, 2022
- $0.25I_0$
- $0.5I_0$
- $0.75I_0$
- $0.866I_0$
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The Correct Option is C
Solution and Explanation
The intensity / of the transmitted light varies directly as the square of the cosine of the angle between the transmission direction of polariser and analyser
$I=I_{0} \cos ^{2} \theta$
Intensity of finally transmitted light after passing through polaroid $B$ is given by $I=I_{0} \cos ^{2} \theta$ (Intensity)
$I=I_{0} \cdot \cos ^{2} 30^{\circ}$
$I=I_{0} 0.75$
$I=0.75 I_{0}$
where, $I_{0}$ is the maximum intensity of transmitted light.
$I=I_{0} \cos ^{2} \theta$
Intensity of finally transmitted light after passing through polaroid $B$ is given by $I=I_{0} \cos ^{2} \theta$ (Intensity)
$I=I_{0} \cdot \cos ^{2} 30^{\circ}$
$I=I_{0} 0.75$
$I=0.75 I_{0}$
where, $I_{0}$ is the maximum intensity of transmitted light.
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Concepts Used:
Polarisation
Light travels in form of transverse EM waves. The underlying oscillation is along directions perpendicular to the propagation direction, in this example, oscillating electric and magnetic fields. Process of restricting the vibration of light waves to one direction is known as Polarisation.
Types of Polarisation:
There are three types of polarisation such as:
- Linear Polarisation in the electric field of light is limited to one single plane that is along the direction of propagation.
- Elliptical Polarisation: In this, both the phase difference and amplitude between the two linear components are not equal.
- Circular Polarisation: The electric field of light follows a circular propagation. The two linear components that exist in the electric field are the same amplitudes but have different phase differences.
Methods of Polarisation of Light:
The few methods of polarisation of Light are:
- Polarization by dispersing
- Polarization by Reflection
- Polarization by Refraction
- Polarization By Transfer