Electrostatics

Good afternoon sir.
Answer is 3rd option.
Explain it sir.

Question image for Good afternoon sir. Answer is 3rd option. Explain

raju nagula

8 Years agoGrade

1 Answer

Arun

Approved Tutor Answer8 Years ago

let the refractive index be RI
angle of from air to glass slab incidence = 45 degrees.
let R1 be the angle of refraction
sin(45 deg)/sin(R1) = Ri
sin(R1) = sin(45 deg)/(Ri)
angle of incidence of the ray on the vertical face of the slab as it travels through it is (90 degrees - R1)
sin(90)/sin(90 deg -R1) = Ri (here angle of refraction should be 90 degrees because we need total internal reflection)
1/cos(R1) = Ri
cos(R1) = 1/Ri

using sin square theta + cos Square theta = 1, we have square(sin(45 deg)/Ri) + square(1/Ri) = 1
square(1/(sqrt(2)*Ri)) + square(1/Ri) = 1
1/(2*square(Ri) + 1/square(Ri) = 1
=3/(2*square(Ri) ) = 1
square(Ri) = 3/2 Hence Ri = sqrt(3/2)