Physics
A student stands between two parallel plane mirrors facing each other. Later, one of the plane mirrors is replaced with a convex mirror.
(a) Why are multiple images formed between two plane mirrors?
(b) When one plane mirror is replaced by a convex mirror, predict how the number and nature of images will change.
(c) If the two plane mirrors are kept perpendicular to each other, what will be the number of images formed?
(d) How many mirrors are used in a kaleidoscope and at what angle are they inclined?
Reflection of Light
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Answer
(a) Multiple images are formed because light undergoes repeated reflections between the two parallel plane mirrors.
Each mirror forms an image of the object as well as of the images formed by the other mirror, resulting in a large number of images (ideally infinite if mirrors are perfectly parallel).
(b) When one plane mirror is replaced by a convex mirror, predict how the number and nature of images will change.
When one plane mirror is replaced by a convex mirror, the number of images decreases greatly.
This is because a convex mirror forms only one virtual, erect, and diminished image and causes the reflected rays to diverge. Therefore, repeated reflections are greatly reduced.
Hence, the images formed become fewer, virtual, erect, and smaller in size.
(c) When two plane mirrors are placed at 90°, the number of images formed is given by
So, 3 images are formed.
(d) A kaleidoscope typically uses three plane mirrors inclined at 60° to each other and this arrangement produces multiple symmetrical patterns due to repeated reflections.
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