Question

A light passes
through air to
medium of refractive
index u. Find the
speed of light in that
medium.
sin r
30°
sini -​

Answer 1

Answer:

Let i be the incident angle and r be the refracted angle

given,

1=

2r⇒

r=

2

i

the refractive index of vacuum is 1 and that of another medium is n

from snell's law,

1sini= nsinr

⇒ sini= nsin

(

2

i

)

2sin (

2

i

) cos (

2

i

) =

nsin

(

2

i

)

⇒

sin (

2

i

)

[2cos (

2

i

) −n]

=

0

sin(

2

i

)= 0= sinπ⇒ i= 2π

[2cos (

2

i

) −n]

= 0⇒ i= 2cos

−1

(

2

n

)

therefore the value of incident angle

=

2cos

−1

(

2

n

)