# 8. Relation between Angle of Incident Emergent Angel Angle fo Deviation and Angle of Prism Physic

#### Byxakbcreative

Aug 4, 2017

When a ray of light falls on a surface of a prism, it deviates from its original path and the ray of light is broken up into seven colours.

It is the constituent color of light. Due to this a spectrum is formed.

The individual colour that is visible in the spectrum , starting from bottom are : Violet, Indigo, Blue, Green, Orange and Red. This can be remembered with this letter ‘VIBGYOR’. Each letter is the starting letter of the color in the spectrum.

Here the relation between incident angle , angle of deviation and emergent angle has been shown. This relation is very important and it comes in the examination.

Watch the video carefully and comment if you have any query.

in Δ MPQ
∠LMQ =∠MPQ+∠PQM
OR ∂= ∂1+∂2 ——– (eqn 1)
Or ∂1 = i1 – r1
Or ∂2 = i2 – r2
In quadrilateral APNQ, We can write
We can write, ∠PNQ = 180- A ——– (eqn 2)( Because ∠APN = ∠AQN = 90)
But for ΔPNQ, we can write ,

∠PNQ=180 – (r1+r2) ——– (eqn 3)
Comparing eqn 2 and eqn 3 we get:
180 – A = 180 – (r1+r2)
∴ A = r1+r2
Now we can write
1+∂2 = (i1 – r1 ) + (i2 – r2)
or ∂1+∂2 = (i1 + i2) – (r1+r2)
or ∂ = (i1 + i2) – A
Which is the reuired equantion.

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