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Question
List four characteristics of the image formed by a concave mirror of focal length 40 cm when the object is placed in front of it at a distance of 20 cm from its pole.
Solution
Using Mirror formula, `1/"v" + 1/"u" = 1/"f"`
Here, u = - 20 cm
f = - 40 cm
`1/"v" = 1/"f"- 1/"u"`
`1/"v" = 1/((-40)) - 1/((-20))=1/20 -1/40 = 1/40 `
⇒ v = 40 cm
Magnification, m =`-"v"/"u" = - 40/((-20)) =2`
As the image distance v, is positive hence the image is formed behind the mirror at a distance of 40 cm from the pole and It's virtual. Also, the magnification is positive and greater than 1 hence image is erect and enlarged.
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