When you enter from bright sunshine into a dark room,you are not able to see clearly for some time. Why?

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

What would have been the colour of the earth's sky if there were no atmosphere?

$A$ prism $ABC,$ with base $BC,$ is placed in four different orientations as shown. $A$ narrow beam of white light is incident on the prism as shown. In which of the following cases,after dispersion,the third colour from the top corresponds to the colour of the sky?

$A$ person cannot see distinctly objects kept beyond $2\, m$. This defect can be corrected by using a lens of power ........ $D$.

$A$ glass slab is placed over a page on which the word $VIBGYOR$ is printed with each letter in its corresponding colour. $(i)$ Will the image of all the letters be in the same place? $(ii)$ If not, state which letter will be raised to the maximum. Give a reason for your answer.