Priyanka B Solutions for Chapter: Light : Reflection and Refraction, Exercise 4: Assignment-2

What are the units of refractive index?

Explain with the help of a diagram why a pencil partly immersed in water appears to be bent at the water surface.

A point source S is placed in water. Name the type of beam of light it emits. This beam of light after coming out from water converges or diverges. Give reason for your answer.

The following table gives the values of refractive indices of a few medium.

Use this table  to give an example of 

(i) a medium pair so that light speeds up when it goes from one of these medium to another.

(ii) a medium pair so that light slows down when it goes from one of these medium of another.

(a) With the help of a ray diagram, show that when light falls obliquely on a side of a rectangular glass slab, the emergent ray is parallel to the incident ray.

(b) Show the lateral displacement on the ray of diagram.

With the help of a ray diagram show that a blue ink dot marked on a sheet of paper appears to be raised. Which phenomenon of light is responsible for this effect?

(a) A ray of light is incident at an angle of $45°$ at the interface of medium (1) and medium (2) as shown in the diagram. Redraw this diagram in your answer sheet and complete it. If the angle of refraction is $30°$, find the refractive index of medium (2) w.r.t. medium (1).$\left[Given: \sin 45°=\frac{1}{\sqrt{2}} and \sin 30°=\frac{1}{2}\right]$

(b) If the second medium is water in place of medium (2), will the angle of refraction increase or decrease? Why? (Refractive index of water$=\raisebox{1ex}{$4$}\!\left/ \!\raisebox{-1ex}{$3$}\right.$).

(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum.

(b) The absolute refractive indices of two media 'A' and 'B' are $2.0 \mathrm{and} 1.5$ respectively. If the speed of light in medium 'B' is $2\times {10}^8 \mathrm{m}/\mathrm{s}$, calculate the speed of light in.

(i) Vacuum       (ii) Medium 'A'.