Home NEET 2020 OPTICS Previous year Questions 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 NEARLY EQUAL TO

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 NEARLY EQUAL TO

NEET 2020

a) \[\frac{A}{2\mu}\]

b) \[\frac{2A}{\mu}\]

c)\[{\mu A}\]

d)\[\frac{\mu A}{2}\]

Diagram:

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 NEARLY EQUAL TO

A RAY IS EMERGES NORMALLY FROM ENERGENT SURFACE.

we know that,

\[A=r_{1}+r_{2}\]

But,\[r_{2}=0\]

\[A=r_{1}\]

According to Snell’s Law,

\[\mu =\frac{\sin i}{\sin r_{1}}\]
\[\mu =\frac{\sin i}{\sin A}\]
As, for thin prism ‘A’ and ‘i’ are too small,
\[sin A\approx A\]
\[sin i\approx i\]
Therefore, above equation becomes,
\[\mu =\frac{\ i}{\ A}\]
\[i=\mu A\]
Answer: Option ‘C’

Milan Tomic

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