Define critical angle with reference to the total internal reflection. Calculate the critical angle for glass-air surface if a ray of light which is incident in air on the glass surface is deviated through $15^{o}$ , when angle of incidence is $45^{o}$ .

Open in App

Solution

Critical angle: It is the angle of incidence beyond which rays of light passing through denser to rarer medium are no longer refracted but reflected totally(total internal reflection).
Let critical angle be $i_{c}$
$sin i_{c} = \frac{1}{u}$ where $u$ is the refractive index of glass.
Also, $\frac{sin i}{sin r} = u$
$i = 45^{\circ}$
$v = 45 - 15 = 30^{\circ}$
$u = \frac{sin 45}{sin 30} = \frac{1 / \sqrt{2}}{1 / 2} = \sqrt{2}$
$sin c = \frac{1}{4} = \frac{1}{\sqrt{2}}$
$c = 45^{\circ}$

Suggest Corrections

Similar questions

Q. (a) Calculate the critical angle for glass air interface if a ray of light incident on a glass surface is deviated through

15^{o}

when angle of incident is

45^{o}

(b) A ray of light travels from denser medium having refractive index

\sqrt{2}

to air, What should be the angle of refracted when angle of incident is

30^{0}

Q. Calculate the critical angle for glass-air interface if a ray of light incident on a glass surface is deviated through

15^{0}

when angle of incidence is

45^{0}

Q. Assertion :A solid glass sphere is placed in air. A light ray entres into the sphere from outside. The ray cannot undergo total internal reflection inside the sphere . Reason: The angle of incidence at

1^{s t}

surface cannot be greater than the critical angle for air-glass system

Q. A ray

R_{1}

is incident on the plane surface of the glass slab (kept in air) of refractive index

\sqrt{2}

at an angle of incidence equal to the critical angle for this air glass system. The refracted ray

R_{2}

undergoes partial reflection and refraction at the other surface. The angle between reflected ray

R_{3}

and the refracted ray

R_{4}

at that surface is :

Glass has refractive index u with respect to air and the critical angle for a ray of light going from glass to air is $θ$ . If a ray of light is incident from air on the glasses with the angle of incidence $θ$ , the corresponding angle of refraction is

Join BYJU'S Learning Program

Define critical angle with reference to the total internal reflection. Calculate the critical angle for glass-air surface if a ray of light which is incident in air on the glass surface is deviated through 15o, when angle of incidence is 45o.

Define critical angle with reference to the total internal reflection. Calculate the critical angle for glass-air surface if a ray of light which is incident in air on the glass surface is deviated through $15^{o}$ , when angle of incidence is $45^{o}$ .