Question

A student claimed that, because of atmospheric refraction (see Discussion Question Q33.2), the sun can be seen after it has set and that the day is therefore longer than it would be if the earth had no atmosphere. First, what does she mean by saying that the sun can be seen after it has set? Second, comment on the validity of her conclusion.

Short answer

Refraction causes Sun to appear even after it sets. The conclusion is valid.

Step-by-step solution

Definition of Refraction

Refraction is the redirection of a wave as it passes from one medium to another.

Pictorial representation of apparent sun after it set

The student meant that even after Sun is set below the Horizon. The sun can be seen due to the refraction of the light through the denser medium of atmosphere.

The student’s argument is true if there is no atmosphere, the apparent Sun cannot be seen due to the refraction of light. If the true position of the Sun is seen, then the day would not be apparently longer.

Thus, Refraction causes Sun to appear even after it sets, and the Conclusion is valid.