Question

A converging lens creates the image shown in:

Is the object distance less than the focal length f, between f and 2f, or greater than 2f?

Answer 1

between f and 2f

because the image real and inverted.

from the figure, magnifocation, m = -1.5

-v/u = -1.5 (here u and v are object and images distances)

v = 1.5*u

now use,

1/u + 1/v = 1/f

1/u + 1/(1.5*u) = 1/f

(1/u)*(1 + 1/1.5) = 1/f

1.67/u = 1/f

==> u = 1.67*f

so, f < u < 2f