(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vaccum. (b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is 2 xx 10^(8) ms^(-1), calculate the speed of light in (i) vaccum (ii) medium 'A'.

(a) State the laws of refraction of light. Explain the term absolute r

1.	(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vaccum. (b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is 2 xx 10^(8) ms^(-1), calculate the speed of light in (i) vaccum (ii) medium 'A'.
Answer» Solution :(a) See POINT Numbers 21 and 23 under the HEADING "Chapter At A Glance". (b) Here `n_(A) = 2.0 and n_(B) = 1.5 and v_(B) = 2 xx 10^(8) ms^(-1)` (i) `because n_(B) = (c)/(v_(B))` HENCE speed of light in VACUUM `c = n_(B) xx v_(B) = 1.5 xx 2 xx 10^(8) = 3 xx 10^(8) ms^(-1)` (ii) `because n_(A) = (c)/(v_(A)) and c = 3 xx 10^(8) ms^(-1)` `therefore v_(A) = (c)/(n_(A)) = (3 xx 10^(8))/(2.0) = 1.5 xx 10^(8) ms^(-1)`