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Question
Two plane mirrors are inclined at angle of 40° between them. Number of images seen of a tiny object kept between them is ______.
Options
Only 8
Only 9
8 or 9
9 or 10
Solution
Two plane mirrors are inclined at angle of 40° between them. Number of images seen of a tiny object kept between them is 8 or 9.
Explanation:
The number of images depends upon the angle between the mirrors and where it is placed. It can be obtained as follows:
n = `(360^circ)/theta`
Here, θ = 40°
∴ n = `(360^circ)/40^circ`
∴ n = 9
n we got is an odd number, so according to rule, again two cases exist,
1. When object is placed asymmetrically, then,
n = `(360^circ)/theta`
Here, θ = 40°
∴ n = `(360^circ)/40^circ`
∴ n = 9
2. When an object is placed symmetrically,
n = `(360^circ)/theta - 1`
∴ n = `(360^circ)/40^circ - 1`
∴ n = 9 - 1
∴ n = 8
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