Q17 of 45 Page 302

Murugan trims his beard while looking into a concave mirror whose focal length is

18 cm. He looks into it from a distance of 12 cm.


i) How far is Murugan’s image from the mirror?


ii) Does it matter whether or not Murugan’s face is closer or farther than the focal length? Explain.


i) Given,


Focal length (f) =-18cm


Object length (u) =-12cm


Image length (v) =?


According to mirror formula,









Thus, the image formed is a virtual image at 36 cm behind the mirror.


ii) The position of the object (Murugan’s face) is of great importance as a concave mirror unlike a convex mirror forms different type of images depending upon the position of the object from the mirror.


Table: Summary of images formed by a concave mirror



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