(a) Total internal reflection: If a light ray enters at one end of an optic fibre coated with a material of low refractive index, it refracted and strikes the walls at angle greater than critical angle. Thus light rays shows multiple reflections, without being absorbed at the side walls.

(b) The teacher knows that Chetan belongs to a below average income group family, so he/she immediatelly arranged the money required to be paid as test fee. His/her caring and helping attitude towards the others resulted in timely help to Chetan’s mother.
Such helping attitude on the part of the person living in the society make it a better society to live in.
(c) Seeing the situation of Chetan’s family and helping attitude of class teacher, doctor took the sympathetic view of the situation, and give the reduction in fee, which is highly appreciable. Such professional ethics of doctor in the society would be an immense help to the person’s belonging to below average income groups.