A right angled isosceles glass prism is made from glass of refractive index 1.5.Show that a ray of light incident normally on
a) one of the equal sides of this prism is deviated through 90 deg
b) The hypotenuse of this prism is deviated through 180 deg
c) Write 2 advantages of this prism over metallic surfaces as reflectors of light

(a) 

In this figure, We have taken PQ as an object. The image in P'Q' rays suffer 90 degree deviation.

(b) 

Here the image P'Q' is inverted and the rays suffer 180 degree deviation.
(c) Advantages:
1- In this prism light is totally reflected but no metallic surface reflects 100 % of incident light.
2-In the prism reflecting properties are permanent and not affected by tarnishing.

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