CBSE Class 12-science Answered

It is assumed the prisms are made up of glass having refractive index 1.5 .

In the first case of isoceless right angle prism , Light ray enters normally through the side AB does not emerges out from side AC .

When the ligh ray makes normal incidence on the face AB , there is no refraction .

Hence light enters inside the glass prism without any deviation . When the light ray incident on face AC ,

angle of incidence will be 45^o that is greater than critical angle 42^o . Hence total internal reflection takes place and

the light ray emerges out of side BC normal to the face BC .

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In the second case of equilateral triangle prism , when light makes normal incidence at the side AB , there is no refraction due to normal incidence.

When the light ray incident on side BC , angle of incidence will be 60^o that is greater than the critical angle 42^o .

Hence , no refraction of light through side BC but total internal reflection takes place.

Hence the reflected light from side BC incident normally at side AC and  emerges out of side AC without any refraction.