shows a small plant near a thin lens The ray shows is one of

shows a small plant near a thin lens The ray shows is one of the principal rays for the lens Each square is 2.5 cm along the horizontal direction but the vertical direction is not to the same scale. Use information from the diagram to answer the following question:

Solution

distance of flower from lens is 5 square blocks => object distance p = 5 x 2.5 cm = 12.5 cm

The ray shown becomes parallel after refraction so we can simply say that the focal length is,
f = (4 + 5) square blocks = 22.5 cm

Now,

1/q + 1/p = 1/f => 1/q +1/12.5 = 1/22.5 => q = - 28.125 cm

negative sign implies image is on the left side of the mirror and it is virtual.