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Refraction Through A Prism 1, Refraction Through A Prism 2, Dispersion Of Light 1 is considered one of the most asked concept.
53 Questions around this concept.
A ray of light is incident at an angle of
A prism is a transparent medium whose refracting surfaces are not parallel but are inclined to each other at an angle A which is also known as angle of the prism.
The angle of deviation -It is the angle between the emergent and the incident ray.
For the above figure
and using
Note-From the above formula, we can say that if we interchange i and e then also we will get the same value of .
As shown in the above figure The graph is a parabola.
If we vary i between
then the value of
decreases
and the value of
increases
And when
and when
This happens when the light ray strikes the second face of the prism at the critical angle for glass - air.
I.e For the prism of refractive index places in the air.
then then e = 90°
Refractive index of prism
As we learned The angle of deviation
For the prism of refractive index
For the first surface, we can write
similarly For the second surface, we can write
using i=e we get
So
- For thin films (i.e
Then
So we get
- condition of no emergence-
i.e A ray of light incidence on a prism of angle A \& Refractive index
This will happen when
where
Dispersion of light -The splitting of white light into its constituent colors or wavelengths is called dispersion of light.
or
angular splitting of a ray of white light into a number of components and spreading in different directions is called diversion of light.
This phenomenon arises due to the fact that the refractive index varies with wavelength.
When white light is incident on the prism it will split itself into its constituent colors as shown in the below figure.
The deviation is given as
Since
So
- Angular dispersion (
It depends upon
- Dispersive power (
where there
we get
where
Condition for deviation without dispersion-
This means an achromatic combination of two prisms in which net(or) resultant dispersion is 0, but and deviation is produced as shown in the below figure.
For the two prisms,
where
Similarly
For the two prisms,
where
Condition for Dispersion without deviation-
A combination of two prisms in which deviation produced for the mean ray by the first prism is equal and opposite to that produced
by the second prism will give a dispersion of light without deviation.
This combination of two prisms is also called a direct vision prism.
As shown in the above figure as emergent rays from the second prism is parallel to the incident white ray of the prism 1.
this will give
For zero deviation ,
and the Angular dispersion is given as
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