5. At what distance from a concave mirror of focal
length 25 cm should an object be placed so that
the size of image is equal to the size of the
object.
Answers
Answered by
1
Answer:
50cm
Explanation:
The size of image is equal to size of object when places at C
It should be placed at 2F =2X25
=50cm
Answered by
10
Given :
Focal length = 25 cm
Magnification = 1
Type of mirror : concave
To Find :
Distance of object from the mirror
Solution :
■ First of all we need to find a relation between u and v. Size of object and size of image are same so we can say that value of magnification is 1.
Formula of magnification for mirror is given by
⇒ m = -v / u
- v denotes distance of image
- u denotes distance of object
⇒ 1 = -v/u
⇒ v = -u .......... (I)
Distance of object can be calculated by using mirror formula which is given by
➠ 1/u + 1/v = 1/f
From the equation (I),
➠ 1/u + 1/u = 1/(-25)
➠ 2/u = -1/25
➠ u = -25 × 2
➠ u = -50 cm
∴ Object should be placed at 50 cm in front of mirror.
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