1.

Critical angle of glass-air is 42^@, then speed of light in glass is .....

Answer»

`3 xx 10^8` m`s^(-1)`
`2 xx 10^8` m`s^(-1)`
`1.5 xx 10^8` m`s^(-1)`
`2.5 xx 10^8` m`s^(-1)`

SOLUTION :Critical angle C=`42^@`
Speed in AIR c=`3xx10^8 ms^(-1)`
Refractive INDEX n=`c/v` but n=`(1)/(sinC)`
`THEREFORE(1)/(sinC)=(3xx10^8)/(v)`
`therefore v=3xx10^8xxsinC`
`=3xx10^8xxsin42^@``=3xx10^8xx0.6691`
`=2.0073xx10^8`
`therefore v~~2xx10^8ms^(-1)`


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