1.

Radius of curvature of concave mirror is 40 cm and the size of image is twice as that of object, then the object distance is :

Answer»

60 CM
20 cm
40 cm
30 cm.

Solution :(d) `f = (R )/(2) = 20 cm`, m = 2 For REAL IMAGE, m = - 2,
By using m = `(f)/(f-u), - 2 = (-20)/(-20 - u) rArr u = - 30 cm`
For virtual image , m = + 2
So, `+ 2 = (-20)/(-20 - u) = - 10 cm`.


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