A concave spherical mirror has radius of curvature of 30 cm. An object was placed 15 cm away of the pole in front of the mirror on the principal axis. Choose the correct option for the position, size and nature of the image formed, respectively.

Correct option is B

The correct answer is (b) At infinity, highly enlarged, real and inverted.
· For a concave mirror, the radius of curvature (R) is 30 cm, thus the focal length (f) is R/2=15 cm.
· The object distance (u) is -15 cm (according to the sign convention, distances measured against the direction of incident light are negative).
· Using the mirror formula 1/f=1/v+1/u
1/15=1/v+1/−15
1/v=1/15+1/15=2/15
v=15/2=7.5 cm
· However, for an object placed at the focal point (15 cm from the pole), the light rays after reflection from the mirror become parallel to the principal axis and meet at infinity.
Information Booster:
· At the focus, highly diminished point-sized, real and inverted: This occurs when an object is placed at infinity.
· Behind the mirror, enlarged, virtual and erect: This occurs when the object is placed between the pole and the focus.
· Between Focus and Centre, diminished, real and inverted: This occurs when the object is placed beyond the center of curvature.