Check sibling questions

Beams of light are incident through the holes A and B and emerge out of box through the holes C and D respectively as shown in the Figure10.3. Which of the following could be inside the box?

fig 10.3.jpg

(a) A rectangular glass slab

(b) A convex lens

(c) A concave lens

(d) A prism



Let us go through the options. 

(a) A rectangular glass slab

  • The emergent beams that come out from C and D are laterally shifted 
  • Emergent rays have undergone lateral displacement  
  • Emergent rays have come out parallel to the incident rays. 

This is consistent with the behaviour of light passing through a glass slab


(b) A convex lens :  The incident rays passing through the holes A and B are parallel. A convex lens makes parallel rays converge onto a single point (the focus), which is not the case here


(c) A concave lens : A concave lens would make parallel rays diverge ,  which is also not the case here .


(d) A prism : A prism splits white light into 7 colours which emerge at an angle after diverging from their original paths. That is also not the case here .

So, the correct answer is (a)

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo