Question

Which method ( snell’s law or critical angle) is more effective for measuring the index of refraction of the plastic? Explain.

Answer 1

The index of refraction for plastic can be caulated by both Snell's law:

n1 sin(theta1) = n2 sin(theta2)

and the critical angle

n1 sin(theta90) = n2 sin(theta-c)

Out of these two, critical angle method is more effective as We already know that at air interface the angle is 90 deg and n = 1.

for the known value if cirtical angle,

n(plastic) = sin90/sin(theta-c)