TOTAL REFLECTING PRISM

A right angled isosceles prism i.e, 45degree-90degree-45degree prism is called a tottaly reflecting prism whenever a ray falls normally on any face of such a prism it is incident on the inside face at 45degree that is at an angle of glass(about 42degree). hence this ray is always totally internally reflected.

THIS PRISM MAY USED IN THREE WAYS :- 1.perriscope:- it is a right angled prism which the rotates the image of an object. here Ic=42.6 degree (where Ic = critical angle ) i is greater than Ic

2.PORROPRISM:-it is also a right angled prism which rotates the image by 180 degree.

so the ray will suffer TIR and the image will get inverted. they are used in BINOCULARS. 3.ERECTING PRISM:-these prism rotates the image of an object by 180 degree. i=45degree is greater than Ic=42.6degree they are used in telescope.