Question

If the image formed by a convex mirror is one third of the object length, when it is placed at 40 cm distance from the mirror, then the focal length of mirror will be -
a. 10 cm
b. 20 cm
C. 30 cm
d. 40 cm​

Answer 1

Answer:

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Explanation:

IT WILL BE 30 CM IF SURE

Substituting ,u=-40cm and f=+40cm in the mirror formula (1/v)+(1/u)=(1/f),wehave(1/v)+(1/-40)=(1/+40),we≥t,v= +20 cmMagnification,m=-(v/u)=-(+20)/(-40)=+(1/2)Magnificationis+(1/2)`, which implies that image is erect, virtual and half in size. Ray diagram is as shown Below,