Question

While performing the experiment to trace the path of a ray of light passing through a glass prism, four students marked the incident ray and the emergent ray in their diagrams in the manner shown below.

The correct path of the rays has been shown by:

Answer 1

Hint:-To solve these kinds of problems we should apply the basic principles of behavior of light rays when it passes through different kinds of mediums like denser and rarer mediums. So, here we should check each diagram that it follows the basic laws of tracing.

Step by step complete solution:-To trace the path of ray of light through prism we should remember two basic laws that-
(a) When light goes from rarer medium to denser medium, it bends towards normal.
(b) When light goes from a denser medium to rarer medium, it bends away from normal.
Here we know that the medium inside prism is denser and outside is rarer.
Now we should check each given option for these two conditions.

For option (1), The incident ray when enters into the prism(Denser medium) then it bends away from the normal line on the left surface of the prism. So it violates the laws.

For option (2), The incident ray does not show any effect of medium when passes through left side of prism( Rarer to denser medium)

For option (3), Incident ray is coming from the right side of the prism. When it enters into the prism, the ray bends towards normal and when it comes out from the prism it bends away from the normal to the left side of the prism.

So option (3) fulfills the conditions that when light goes from rarer medium to denser medium, it bends towards normal and when light goes from a denser medium to rarer medium, it bends away from normal.

So option (3) shows the correct path of ray passing through prism.

Note:-Sometimes, we don’t focus on the direction of the incident line and apply all the basic principles correctly. But the final answer goes wrong because of the mistake in observing the right direction of the incident ray.