 ×     #### Thank you for registering.

One of our academic counsellors will contact you within 1 working day.

Click to Chat

1800-1023-196

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
```
what is maximum angle of deviation? explain with diagram

```
7 years ago

```							PRISM
A prism has two plane surfaces AB and AC inclined to each other  as shown in following  figure. A is called the angle of prism or  refracting angle. (i)    Refraction Through A A light ray striking at one face of a triangular glass prism gets  refracted twice and emerges out from the other face as shown above. The  angle between the emergent and the incident rays is called the angle of  deviation (D). The angle between the two refracting faces involved is  called the refracting angle (A) of the prism.
From AXY, we have:           A + (90° – r1) + (90° – r2) = 180°
As     r1 + r2 = A                                               (i)
Deviation D = (i – r1) + (e – r2)
D = (i + e) – (r1 + r2)
D = i + e – A
A + D = i + e                                      (ii)
We also have two equations from Snell''s Law at X & Y. (i)     Angle of Deviation
It can be easily seen that if we reverse the emergent ray, it goes  back along the same path. The angles of incidence and emergence get  interchanged but the angle of deviation remains same. Hence the same angle of deviation D is possible for two different angles of incidence :

θ1 and θ2, where θ1 + θ2 = A + D.
(ii)   Minimum Deviation
The angle of deviation is  minimum when the path of light ray through the prism is symmetrical.  i.e., angle of incidence = angle of emergence (iii)       Grazing Incidence
When i = 90°, the incident ray grazes along the surface of the prism  and the angle of refraction inside the prism becomes equal to the  critical angle for glass - air. This is known as grazing incidence

(iv)       Grazing EmergenceWhen  e = 90°, the emergent ray grazes along the prism surface. This happens  when the light ray strikes the second face of the prism at the critical  angle for glass - air. This is known as grazing emergence.

(v)       Maximum Deviation

The angle of deviation is same for both the above cases (grazing  incidence & grazing emergence) and it is also the maximum possible  deviation if the light ray is to emerge out from the other face without  any total internal reflection.

(vi)     Dispersion of Light

When a ray of light passes through a prism, it splits up into rays  of constituent colours or wavelengths. This phenomenon is called  dispersion of light.
The refractive index of a medium is different for light rays of  different wavelengths. Larger the wavelengths, the lesser is the  refractive index.
i.e.    mred < mviolet because 1red > 1violet

A ray of white light passing through a prism gets splits into  different colours because the deviation is more for violet and less for  red. This phenomenon is known as dispersion. For a prism with very small refracting angle A, the deviation D is given by:
d >> (m-1)A
Hence deviaiton of violet = Dv = (μv - 1)A,
and for red = Dr = (μr – 1)A
The angle between the red and violet rays is known as the angle of dispersion.The angle of dispersion = f = Dv - Dr =  (mv - mr)A This phenomenon arises due to the fact that refractive index varies  with wavelength. It has been observed for a prism that μ decreases with  the increase of wavelength, i.e.
mviolet > mred (viii)    Deviation without Dispersion
This mean an  achromatic combination of two prisms in which net or resultant  dispersion is zero and deviation is produced. For the two prisms, Where w and w'' are the dispersive powers of the two prisms and d and d'' their mean deviations.
(ix)      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 is called a direct vision prism. This combination produces  dispersion without deviation.
For deviation to be zero, (d + d'') = 0 ```
7 years ago
Think You Can Provide A Better Answer ?

## Other Related Questions on Wave Motion

View all Questions »  ### Course Features

• 101 Video Lectures
• Revision Notes
• Previous Year Papers
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Test paper with Video Solution  ### Course Features

• 110 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions