Question
Physics Question on Ray optics and optical instruments
A wide slab consisting of two media of refractive indices n1 and n2 is placed in air as shown in the figure. A ray of light is incident from medium n1 to n2 at an angle θ, where sinθ is slightly larger than n11. Take refractive index of air as 1.Which of the following statement(s) is(are) correct?
The light ray enters air if n2=n1
The light ray is finally reflected back into the medium of refractive index n1 if n2<n1
The light ray is finally reflected back into the medium of refractive index n1 if n2>n1
The light ray is reflected back into the medium of refractive index n1 if n2=1
The light ray is finally reflected back into the medium of refractive index n1 if n2<n1
Solution
sin(θ)>n11 … (i)
And n1sin(θ)=1×sin(r) … (ii)
⇒sinr>1
⇒ refraction into air is not possible
Therefore correct options are :
(B) The light ray is finally reflected back into the medium of refractive index 𝑛1 if n2<n1
(C) The light ray is finally reflected back into the medium of refractive index 𝑛1 if n2>n1
(D) The light ray is reflected back into the medium of refractive index 𝑛1 if 𝑛2 = 1