Question

2
7. Light travels with velocities 2 x 108 m s-1 and 2.5 x 108 m s-1 through two different media. The critical angle
of the two media is
(1) sin (5)
(2) sin (
(3) sin"
(4) sin (2)​

Answer 1

Answer:

${ \sin }^{ - 1}( \frac{4}{5})$

Explanation:

Here the medium with more velocity (2.5×10^8m/s) is rarer medium

Another medium with relatively less velocity (2×10^8m/s) is denser medium

So to form critical angle, the ray should travel from denser (n1) to rarer (n2)

i=c

r=90°

n1= 3×10^8/2×10^8=3/2=1.5

n2=3×10^8/2.5×10^8=6/5=1.2

from Shell's law,

n1 sin i=n2 sin r

1.5 sin c=1.2 sin 90°

sin c=1.2/1.5

sin c=4/5

=>c=sin^-1(4/5)

Answer 2

Answer:

sin inverse of 5/2 or sin inverse of 1.25