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` m/s, calculate the speed of light in:
(i) vacuum (ii) medium 'A'.

Explanation

`n_A = 2.0 , n_B =1.5 ,` speed of light in medium `B, v_B = 2xx 10^8` m/s
`(i) n_B = c/v_B`
`therefore c = n_B v_B`
`= 1.5 xx 2 xx 10^8 `m/s `=3xx10^8 ` m/s
(ii) `n_A = (c)/(v_A)`
`therefore v_A = (c)/(n_A) = (3xx 10^(8) m//s)/(2) = 1.5 xx 10^(8) ` m/s