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Topic: Refraction through a prism· Optics

A ray is incident at an angle of incidence i on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is μ, then the angle of incidence is nearl…

A ray is incident at an angle of incidence \(i\) on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is \(\mu\), then the angle of incidence is nearly equal to :

1. \(\frac{A}{2\mu}\)

2. \(\frac{2A}{\mu}\)

3. \(\mu A\)

4. \(\frac{\mu A}{2}\)

1 answer

Best answer

Answer: 3. \(\mu A\)

For a small-angle prism, with emergent ray normal to the second face, the angle of refraction at the second face is 0.

  1. Since \(r_1+r_2=A\) and \(r_2=0\), we get \(r_1=A\).
  2. Snell's law at the first face: \(\sin i=\mu\sin r_1\).
  3. For small angles, \(i\approx\mu r_1=\mu A\).

Answer: option 3.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report
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