A concave mirror forms a real image at 80 cm for an object at 40 cm. The object is shifted to 50 cm. Find the new image distance in centimetres.
Physics · Geometrical optics · spherical mirror
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Question

A concave mirror forms a real image at 80 cm for an object at 40 cm. The object is shifted to 50 cm. Find the new image distance in centimetres.

G1 Physics · Accepted Answer

Initial data give f=40×80/120=80/3 cm. New v=f u/(u−f)=(80/3×50)/(50−80/3)=4000/70≈57.14 cm.