- #1

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**Question**

A laser beam travels from air into a symmetrical prism at right angles close to its upper edge. The refractive index of the prism material n = 1.4 and its angle is 30 degrees.

**i)**

Calculate the critical angle for the prism-air interface.

**Possible Answer:**

Critical angle = arcsine(1/n)

arcsine(1/1.4)

= 45.585 degrees

**ii)**

After passing through the prism, what angle does the beam make with the incident ray?

**Possible Answer:**

Sine Angle = (n of prism)(Sine30)/n of air

= ((1.4)(Sin30))/1.0

Sine Angle = 0.7

Angle = 44.427 degrees

Are these correct?