An object placed at 20cm in front of a concave mirror produces three times magnified real image. What is the focal length of the concave mirror?A. 15cmB. 6.6cmC. 10cmD. 7.5cm

An object placed at 20cm in front of a concave mirror produces three t

1.	An object placed at 20cm in front of a concave mirror produces three times magnified real image. What is the focal length of the concave mirror?A. 15cmB. 6.6cmC. 10cmD. 7.5cm
Answer» Correct Answer - A We know that, linear magnification, `m=(f)/(f-u)` Given object displaced, u=-20cm m=-3 (`therefore "all images aer inverted"`) `So, -3=(f)/(f-(-20))` `-3=(f)/(f+20) Rightarrow -3f-60=f` `4f=-60 Rightarrow f=-(60)/(4)=-15cm` Since, mirror is concace, f=-15cm

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An object placed at 20cm in front of a concave mirror produces three times magnified real image. What is the focal length of the concave mirror?A. 15cmB. 6.6cmC. 10cmD. 7.5cm

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