Question

(i) Why does the sky appear dark to an astronaut in space?
(ii) Which part of an eye adjusts the size of its pupil?

Answer 1

i) The sky appears dark to an astronaut in space because of no atmosphere to undergo no scattering of sunlight. Scattering is a phenomenon by which beam of light is redirected in many different directions on interaction with particle of matter , say atmosphere, where the suspended particles can redirect light in different directions.
In space there is no atmosphere or particle to scatter light. Hence sky appears dark to astronaut.

ii)The iris adjusts the size of the pupil. It does so by ciliary muscles that contract or expand depending on the amount of light the pupil needs to process images.