Advertisements
Advertisements
प्रश्न
What is the angle of polarisation and obtain the equation for an angle of polarisation?
Advertisements
उत्तर
-
The angle of incidence at which the reflected beam is plane polarised light is called polarising angle (ip)
Polarisation by reflection - When ordinary light is incident on the surface of a transparent medium, the reflected light is partially plane polarised.
- The extent of polarization depends on the angle of incidence.
- For a particular angle of incidence, the reflected light is found to be plane polarised.
- The angle of incidence at which a beam of unpolarised light falling on a transparent surface is reflected as a beam of plane polarised light is called polarising angle or Brewster’s angle. It is denoted by i
- At polarising angle, the reflected transmitted rays are perpendicular to other.
ip + 90° + rp = 180°
rp = 90° – ip
From Snell’s law
`(sin "i"_"p")/(sin "r"_"p")` = n - Where n is the refractive index of the medium with respect to air.
- Substitute the value of r from Equation, we get,
`(sin"I"_"p")/(sin (90^circ - "i"_"p")) = (sin "i"_"p")/(sin "r"_"p")` = n
tan ip = n
This relation is known as Brewster’s law.
APPEARS IN
संबंधित प्रश्न
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.
Show, with the help of a diagram, how unpolarised sunlight gets polarised due to scattering.
What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5)
When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation.
A ray of light passes from a vacuum to a medium of refractive index (μ). The angle of
incidence is found to be twice the angle of refraction. The angle of incidence is _______.
A) `cos^(-1)(mu/2)`
B) cos−1(μ)
C) `2 cos^(-1) (mu/2)`
D) `2 sin^(-1) (mu/2)`
State two uses of Polaroid.
A ray of ordinary light is travelling in air. It is incident on air glass pair at a polarising angle of 56°. Find the angle of refraction in glass.
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.
Light transmitted by Nicol prism is ______.
The transverse nature of light is shown in ______.
What is polarisation?
State and obtain Malus’ law.
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?
A plane mirror produces a magnification of
For the same objective, find the ratio of the least separation between two points to be distinguished by a microscope for light of 5000 Å and electrons accelerated through 100 V used as the illuminating substance.
To ensure almost 100 per cent transmissivity, photographic lenses are often coated with a thin layer of dielectric material. The refractive index of this material is intermediated between that of air and glass (which makes the optical element of the lens). A typically used dielectric film is MgF2 (n = 1.38). What should the thickness of the film be so that at the center of the visible spectrum (5500 Å) there is maximum transmission.
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 ______.
