Help Snells law. (1 Viewer)

Shoom

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Problem

Angle of Incidence is 40 calculate the angle of refraction. Light enters perspex from air.

Refractive index of perspex= 1.46 light = 1
Velocity of perspex in medium = 2 x 10^8 light = 3 x 10^8

Using snells law

Sin40/Sinr=3x10^8/2x10^8

Sinr= 2x10^8xSin40/3x10^8 = 0.4285

Shift Sin 0.4285= 25.37 degrees.


HOwever when I use
Sini/Sinr=n2/n1

Sin40/Sinr= 1.46/1

Sin40/1.46= Sin r = 0.4402
Shift Sin 0.4402=26.12 degrees, why do I get this difference, when snells law states V1/v2=sini/sinr=n2/n1

Will I get this wrong in exam if I use either method but get a different answer?
 

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