Q.

A man of height 170cm wants to see his complete image in a plane mirror (while standing). His eyes are at a height of 160 cm from the ground.


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a

Minimum length of the mirror = 80 cm

b

Minimum length of the mirror = 85 cm

c

Bottom of the mirror should be at a height 80 cm or more

d

Bottom of the mirror should be at a height 85 cm 

answer is B.

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Detailed Solution

Concept: The simplest way to solve this problem is to calculate half a man's height to determine the minimum length of the mirror. To determine the bottom location of the mirror, you need to also calculate half a man's height from the ground.
We have the data from the givens,
Man's height is 170 cm.
The distance between a man's eyes and the ground is 160 cm.
There are two ways to fix this issue.
The method I: direct approach
In order to see one's entire body height in a plane mirror, the mirror must be at least,
Lmin=h2
where H is the person's height.The height of the man is
 170 cm tall.
As a result, we determine that the mirror's minimum length is
Lmin=1702
Lmin=85cm
Hence, the correct option is  2 and 3.
 
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