Physics, asked by 23079, 10 months ago

62. A ray of light incident on the face AB of
an isosceles triangular prism makes an
angle of incidence i and deviates by angle
B as shown in the figure. Show that in the
position of minimum deviation ZB = Za.
Also find out the condition, when the
refracted ray QR suffer total internal
reflection
C All India 2019​

Answers

Answered by mad210216
4

Position of Minimum deviation ZB = Za

i.e ∠β = ∠α = 60°

Explanation: Here α = 60° (for isosceles triangle)

  • Now r₁ = 90°- β from diagram
  • and r₂ = β - 30° from diagram
  • and for minimum deviation angle
  • r₁ = r₂
  • 90°-β = β -30°
  • 2β = 120°
  • β = 60° = α Hence proved i.e ZB =Za.
  • For TIR
  • r₂= Ic
  • r₂ = 30°
  • now according to condition of TIR
  • 1/ SinIc ≤ u
  • 1/Sin30° ≤ u
  • u≥ 2
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