Question

(I)Why does the sky appear darker to an astronaut in space?
(II)Which part of an eye adjusts the size of its pupil?

Answer 1

Hint: Scattering of light by dust or gas molecules, water vapours etc is what causes colours appear in the sky. Absence of this due to these obstacles will not allow scattering of light. Additionally, the human eye is a crucial organ used for vision. Its parts like iris and ciliary muscles help it to adjust and view properly.

Complete step by step answer:
(i)Space is defined as a continuous area or expanse which is free, available, or unoccupied. So in space, there is no atmosphere or any other object like on earth.

When light propagates on earth it undergoes a number of phenomena like deviation, refraction etc. One such phenomenon, that is scattering of light, also known as deviation defined as the phenomenon in which light rays get deviated from its straight path on striking an obstacle like dust or gas molecules, water vapours etc. This scattering of light is responsible for the colours we see in the sky.

But in space, there is no atmosphere, i.e. no obstacle like dust or gas molecules, water vapours etc to obstruct the path of light and thus cause scattering of light. Thus due to the absence of atmosphere in space, the phenomena of scattering of light does not take place. As a consequence of all this, the sky appears darker to an astronaut in space.

(ii)The human eye is an amazing organ that responds to light in different ways in different circumstances. Working as a conscious sense organ, the human eye allows vision for humans. There are rod and cone cells in the retina, which allow conscious light perception and vision. Additionally, they also permit colour differentiation and the perception of depth. The iris in the human eye adjusts the size of the pupil. It performs this function by the help of ciliary muscles, which tend to contract or expand depending on the amount of light the pupil needs to process images. It is a very crucial part of the human body.

Note: Students should first explain briefly the underlying facts and reasons for the asked question. And then elaborate them with reference to the provided scenario later; in order to support their answer. And thus it will help them justify their answer better.