(i) An astronaut in space sees the sky as dark because there is no atmosphere to disperse sunlight. Scattering is a phenomenon in which a beam of light is diverted in many distinct directions when it interacts with particles of matter, such as suspended particles in the atmosphere.
There is no atmosphere or particle in space to scatter light. As a result, the sky seems gloomy to the astronaut.
(ii) The iris controls the pupil size. It accomplishes so through ciliary muscles, which contract or expand depending on how much light the pupil requires to comprehend images.
Final Answer:
Hence,
(i) The sky appears dark to an astronaut in space because there is no scattering of sunlight.
(ii) Iris adjusts the size of its pupil.