1.

Light travels in two media A and B with speeds 1.8 xx 10^(8) ms^(-1) and 2.4 xx 10^(8) ms^(-1) respectively. Then the critical angle between them is :

Answer»

`SIN^(-1)((2)/(3))`
`tan^(-1)((3)/(4))`
`tan^(-1)((2)/(3))`
`sin^(-1)((3)/(4))`

Solution :(d) Here, `v_(A) = 1.8 XX 10^(8) ms^(-1)`
`v_(B) = 2.4 xx 10^(8) ms^(-1)`
Light travels slower in denser medium. Hence medium A is a denser medium and medium B is a rarer medium. Here, light travels from medium A to medium B. l=Let C be the critical angle between them.
`thereforeC = A_(mu_(c))=(1)/(B_(mu_(A)))=(mu_(B))/(mu_(A))=(v_(A))/(v_(B)).`
Refractive INDEX of medium B w.r.t medium A is
`therefore sinC=(v_(A))/(v_(B))=(1.8xx10^(8))/(2.4xx10^(8))=(3)/(2)`
`RARR "" C = sin^(-1)((3)/(4))`.


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