Question

if focal length of the concave mirror is 20cm, we get the virtual image of the object placed at a distance _____ than 20cm. ( )

(a) less (b) more (c) equal (d) double​

Answer 1

Answer:

less

Explanation:

the object must be placed at 20/3 from the mirror to get virtual image.

Answer 2

Given:

Focal length = 20cm

To Find:

To get the virtual image the object should be placed at what distance

Explanation:

• The virtual image is formed when the object is placed between the pole and the focus.

• In this case the first ray will go through the center of curvature and second will  go through focus and reflected back parallel.

• when extended back the two lines the point of intersection is behind the mirror.

• Therefore the image formed is magnified, upright , virtual and less then the focal length.

Hence answer = less