Question

Which surfaces are known as refracting surfaces in the glass prism?
(A) Rectangular surfaces
(B) Triangular surfaces
(C) Circular surfaces
(D) Cylindrical surfaces

Answer 1

Hint:In this question, we are supposed to find out what surfaces are known as refracting surfaces in a glass prism. In a glass prism, we always consider refraction of light to at faces which are transparent. Consider any prism, there you will find two kinds of surfaces, accordingly determine which face will be the refracting surface.

Complete answer: Consider a triangular prism. It is the most traditional prism. Colloquial use of prism generally refers to the triangular prism. This prism has a total of five surfaces, out of which two are triangular and the rest three are rectangular. The two triangular faces are opposite to each other. These triangular faces are translucent. So, we use the rectangular faces to study the refraction of light. Hence, in a triangular glass prism, the refracting surfaces are the rectangular surfaces.

Now, consider a cylindrical glass prism. This glass prism has one cylindrical shaped surface and the top and bottom are the circular surfaces. The two circular surfaces of the cylindrical glass prism are translucent and the cylindrical surface is transparent. This cylindrical transparent surface is used for the refraction of light. Hence, in a cylindrical glass prism, the refracting surface is the cylindrical surface.

Hence, surfaces which are known as refracting surfaces in the glass prism are rectangular surfaces and cylindrical surfaces.

Hence the correct options are (A) and (D).

Note:Whenever we deal with a prism, the surface which is used for the refraction of light is always the transparent surface and not the translucent surface. Also remember that a particular prism has its own refractive index. This refractive index is found using Snell 's Law. It tells you how fast a light travels in a medium. In case of a prism, the Snell’s Law also gives you the angle by which the light is deviated due to refraction.