Critical angle

Electricity and Magnetism Level 1

The critical angle is the angle of incidence above which total internal reflection occurs. If the speed of light is 1.5 × 1 0 8 m/s 1.5 \times 10^8\text{ m/s} in a particular medium, then what is the critical angle of the light passing through this medium into the air?

The speed of light in the air is 3.0 × 1 0 8 m/s . 3.0 \times 10^8\text{ m/s}.

60. 0 ∘ 60.0^\circ 30. 0 ∘ 30.0^\circ 45. 0 ∘ 45.0^\circ 15. 0 ∘ 15.0^\circ

Lakshan Dumpa by Lakshan Dumpa , 24, India

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2 solutions

Arijit Banerjee
Mar 1, 2014

Refractive Index of the medium(n)= (3 * 10^8)/(1.5 * 10^8) =2 (according to snell's law) then we know that critical angle is = sin^-1(1/n) = 30 degrees

6 Helpful 0 Interesting 0 Brilliant 1 Confused

I calculate correctly but instead of selecting 30 degree I selected 45degree

padma vathi - 7 years ago
Sethu Raman
Feb 28, 2014

SPEED OF LIGHT /SPEED OF LIGHT IN AIR=1.5 10^8/3 10^8=1/2 CRITICAL ANGLE=sin(theata)=1/2=30(degree)

3 Helpful 0 Interesting 0 Brilliant 0 Confused

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