Light: Shadows and Reflections MCQs for UPSC Prelims
120 practice questions covering Light: Shadows and Reflections, organised into 0 topics.
120 questions include a written explanation.
Pick a topic below, or try the samples first.
Sample questions
Q1
medium
Which of these capital letters, written on a card facing a plane mirror, looks exactly the same in its reflection?
AR
BB
CP
DA
Show answer and explanation
Correct answer: D - A
A mirror swaps the left and right halves of a letter. The letter A has matching left and right halves, so the swap leaves it looking unchanged. B, P and R all have their curves on one side only, so in the mirror those curves move to the other side and the letters look reversed.
Q2
hard
The three mirror strips of a kaleidoscope are replaced by three strips of plain cardboard of exactly the same size. Looking into the tube, a person will now see
Aa brighter pattern than before
Bthe pattern turned upside down
Cjust the few coloured pieces, with no repeating pattern
Dthe same pattern in black and white
Show answer and explanation
Correct answer: C - just the few coloured pieces, with no repeating pattern
The repeating pattern comes entirely from reflections between the mirrors, and rough cardboard cannot reflect regularly, so only the actual pieces are seen. The tube also becomes darker rather than brighter, since cardboard soaks up light. With no reflections there is no pattern left to appear in another colour or another position.
Q3
medium
A small coin held close to a torch throws a shadow on the wall that is far bigger than the coin itself. This happens because
Athe coin becomes bigger in the dark
Bthe wall makes the shadow bigger
Clight bends round the coin and spreads out
Dlight spreads out from the torch, so the blocked region keeps widening
Show answer and explanation
Correct answer: D - light spreads out from the torch, so the blocked region keeps widening
The torch light travels outwards as a widening cone, so the patch it cannot reach also widens as it goes towards the wall. The coin itself does not change size, and light does not bend round it. The wall only receives the shadow; it does nothing to enlarge it.
Q4
medium
The beautiful patterns seen in a kaleidoscope are formed because the coloured pieces are
Areflected again and again between the mirror strips
Bmade to glow by the mirrors
Cbroken into smaller pieces by the tube
Dseen through a tiny hole one at a time
Show answer and explanation
Correct answer: A - reflected again and again between the mirror strips
Each mirror reflects the pieces, and those reflections are reflected again by the other mirrors, so a few pieces appear many times over in a regular arrangement. The pieces do not glow, and nothing inside breaks them. Looking through a small opening does not by itself repeat anything.
Q5
easy
An object is moved closer to a torch while the screen behind it is not moved. Its shadow on the screen becomes
Acoloured
Blarger
Csmaller
Dexactly the same size
Show answer and explanation
Correct answer: B - larger
Light spreads out as it leaves a torch, so an object nearer the torch blocks a wider slice of the spreading light and the dark patch on the screen grows. Moving the object away would make the shadow smaller. The size clearly changes, and a shadow never takes on a colour.
Q6
easy
Reflection from a smooth, polished surface, which gives a clear image, is called
Ascattering by dust
Babsorption of light
Cregular reflection
Dirregular reflection
Show answer and explanation
Correct answer: C - regular reflection
On a smooth surface the reflected light keeps its neat arrangement, so a clear image is formed, and this is called regular reflection. Irregular reflection happens on rough surfaces, where the light is thrown in many directions and no image forms. Absorption means light is taken in, and scattering by dust happens in the air, not at a polished surface.
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