Question

The velocity of light in a medium is 1.5 x 108 m/s. the critical angle of the medium for a ray going from the medium into air is:

Answer 1

Answer:

30 degrees

Explanation:

Answer 2

Given:

• The velocity of a medium = 1.5 × $10^8$ m/s

To Find:

• The critical angle of the medium for a ray going from the medium to air.

Solution:

The velocity of light in air =  3 × $10^8$ m/s

By snell's law we know that,

sin (i)/sin(r) = $n_2/n_1$ = $v_1/v_2$ → {equation 1}

On substituting the values in equation 1 we get,

⇒ sin (c)/1 = (1.5×$10^8$)/(3 × $10^8$ ) {sin(r) = 1 since sin (90°) = 1}

⇒ sin (c)/1 = 1/2

⇒ sin (c) = sin (30°) { sin 30° = 1/2}

⇒ c = 30°

∴ The critical angle of the medium for a ray going from the medium to air = 30°