00:01
In this question, it is given that the focal length of a concave mirror which is equal to 40 .0 cm.
00:15
And also given that image is upright and four times a size of the object.
00:23
So we can write magnification m equal to minus v by u, which is given as four.
00:36
Then the relation between the object distance and the image distance.
00:42
Here v is image distance and u is object distance.
00:49
It can be written as minus v equal to 4u which implies v equal to minus 4u and the mirror equation which can be written as 1 by f equal to 1 by v to 1 by v to plus 1 by u.
01:10
So on substituting this relation it will become 1 by minus 4 u plus 1 by u.
01:20
Then we can apply sign convention therefore the relation will become the object distance is negative image distance is positive and the focal length of the concave mirror is negative.
01:45
Therefore it will become 1x minus f equal to 1 by minus 4 minus u plus 1 by minus u.
02:00
It can be written as 1 by 4 u minus 1 by u...