Question

An object is placed in front of a spherical mirror whose 2 times magnified images are formed on the screen. Then choose the CORRECT option:-
A. Mirror is concave m=+2
B. Mirror is concave m=-2
C. Mirror is convex m=+2
D. Mirror is convex m=-2

Answer 1

Hint:Recall the different types of images formed by the concave and convex mirrors. Check which type of mirror forms the real and enlarged image of the object when the object is placed in front of the mirror. Check whether the image formed is inverted or erect to determine the sign of the magnification.

Complete step by step answer:
-We have given that an object is placed in front of a spherical mirror. The magnification of the image is 2 times the size of the object and the image of the object is formed on the screen.Since the image of the object is formed on the screen, it must be a real image of the object. But the convex mirror does not form the real and magnified image. The image formed by the convex mirrors is always virtual and diminished.Hence, the options C and D are incorrect.
-The real image of the object is formed by the concave mirror.For the concave mirror to form a real image, the object should be place at a distance from the mirror which is greater than the focal length of the mirror.But the image formed by the spherical mirror is real as well as enlarged. For the concave mirror to form real and enlarged images, the object should be placed between the focus of the mirror and the centre of curvature of the mirror.The object placed between the focus and centre of curvature of the concave mirror will form a real, enlarged and inverted image.Since the image is inverted, the magnification of the image should be -2.Therefore, the image formed by the spherical mirror will be on the screen and is 2 times magnified if the spherical mirror is a concave mirror with magnification -2.

Hence, the correct option is B.

Note: The sign of the magnification of the concave mirror is negative for the inverted image because the height of the image formed will be measured on the negative scale as the image formed is inverted. The sign is taken positively for the erect image as the size of the image is measured on the positive scale.