Question

28. Give reasons:
a) Can absolute refractive index of any material be less than 1.
b) We are advised not to see the sun directly.
c) When a ray of light passes through centre of curvature of a concave
mirror, it gets reflected through the same path.​

Answer 1

Answer:

1a)As Anthony Atkielski correctly wrote in an answer collapsed for unknown reason, a refractive index below 1 means a speed above the speed of light in vacuum, which is, according to theory of relativity, the highest possible speed.

This is so because refractive index is DEFINED as “speed of light in vacuum/speed of light in medium“.Assume a refractive index of 1.5 ( glass), you gather speed of light in glass as 200.000 km/s, i.e. 300.000 km/s divided by 1.5.Any medium having a refractive index below 1 would violate something which has that often be proven that we can quite savely assume it is a nature of law.

b)Sun is a strong radiator of UV light also, apart from visible light. This is amplified by our eye lens that could damage the sensitive retina. Sun releases UV rays and cause cancer. Direct rays on eyes make a bright shine and put pressure on eyes therefore we are not advised to see sun directly.

c)A ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path because when ray of light passes through centre of curvature of a concave mirror it strikes the mirror at 90 degree that is incident ray coincides normal therefore angle of incidence = 0 so, according to law of ...

Explanation: