Assertion (A): In case of a rainbow, light at the inner surface of the water drop gets internally reflected.
Reason (R): The angle between the refracted ray and normal to the drop surface is greater than the critical angle.
Answer
Let’s look at how a rainbow is formed
- After rain , there are many tiny droplets of water still in the air
- When sunlight falls on these droplets
- These droplets act as tiny prisms
- When sun rays fall on these droplets, the rays get first refracted , then internally reflected and then refracted again
- Due to this different colors of sunlight are bent at different angles and we are able to see a spectrum in the form of a rainbow
Since light at the inner surface gets internally reflected, Assertion is true
For critical angle,
- Total internal reflection only takes place if the light from a denser medium to a lighter medium strikes at an angle of incidence larger than the critical angle .
- If the angle between the refracted light and the normal to the drop surface is greater than a critical angle ( which is 45 degrees), the light reflects off the back of the drop .
- If the angle between the refracted light and the normal to the drop surface is less than the critical angle , the light will simply pass through .
Therefore, r easoning is also a true and correct explanation of assertion .
Thus,
- Assertion is True
- Reason is True
- And reason is the correct explanation for the assertion.
So, the correct answer is (a)
