Question

A teacher gives a convex lens and a concave mirror of focal length about 12 cm each to

her student and asks her to find their focal length by obtaining the image of a distant

object. The student uses a distant tower as the object and obtains its sharp image one

by one on a white screen. The distances l1 and l2 between the lens/mirror and the

screen in the two cases and the nature of their respective images are likely to be




(12 cm, 12 cm) and (erect, erect)

(b) (12 cm, 24 cm) and (erect, erect)

(c) (12 cm, 24 cm) and inverted, inverted)

(d) (12 cm, 12 cm) and (inverted, inverted)

Answer 1

The option is D

Since, the focal length of each is of 12cm , then the image of distant object is formed at the focus.

Thus, the image distance of each is 12 cm.

Moreover, the image is of point sized and INVERTED when the image is at infinity.

Thank You.