Question

Assertion: The images formed by total internal reflections are much brighter than those formed by mirrors or lenses.
Reason: There is no loss of intensity in total internal reflection.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
(B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
(C) Assertion is correct but Reason is incorrect
(D) Both Assertion and Reason are incorrect.

Answer 1

Hint
To answer this question, we have to see the effect of loss of intensity on the brightness of the image. Then, we need to compare the loss of intensity in the case of mirrors and lenses with that in the case of total internal reflection.

Complete step by step answer
When the rays of light from an object fall on the surface of a mirror, along with the reflection on its surface, there is always some amount of refraction into the other medium.
Likewise, in the case of lenses, when the rays of light from an object fall on their surface, along with the refraction of the light into the other medium, there is always some amount of reflection about the surface.
So, in both the above cases, there is partial reflection and partial refraction.
Therefore the intensity of the incident ray of light is distributed into the intensity of the reflected light and that of the refracted light.
But, in the case of total internal reflection, all the light rays falling on the surface get reflected back into the same medium, and there is no partial refraction. Therefore, $100\%$of the intensity of the incident light appears as the intensity of the reflected light. Thus, there is no loss of intensity in the case of total internal reflection.
So, this means that the Reason is correct.
Now, as there is no loss in the intensity, the images formed by total internal reflections are much brighter than those formed by mirrors or lenses. This is because in the latter case, there is always some intensity loss due to partial reflection or refraction.
So, this means that the Assertion is also correct.
As we used the Reason to prove the Assertion, so the Reason is the correct explanation for the Assertion.
Hence, the correct answer is option (A).

Note
As there is no loss in the intensity in the case of total internal reflection, this phenomenon is used in many optical devices. The optical fibre cable, which is used to transmit the data over long distances, is based on this phenomenon. Due to the total internal reflection, the signal strength is not reduced over long distances. This phenomenon is also used in other optical instruments, like telescopes, periscopes, spectroscopes etc.