If the critical angle for total internl reflection from a medium to vacuum is `30^@`then velocity of light in the medium is:

Explanation

Critical angle `=c=30^(@)`
`m=1/(sinc)=1/(sin30)`
`mu=1/(1//2)=2`
Also `mu=c/v`
`v=c/(mu)`
`v=(3xx10^(8))/2`
`v=1.5xx10^(8)m//s`