Calculate Focal Length Problems Mirror Equation

Rays from Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed so that size of its image is equal to the size of the object?

• 15 cm in front of the mirror

• 30 cm in front of the mirror

• more than 30 cm in front of the mirror

• between 15 cm and 30 cm in front of the mirror

Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image? (Assume that the image is formed behind the mirror.)

• + 40 cm from the mirror, real and inverted

• - 40 cm from the mirror, virtual and erect

• - 80 cm from the mirror, real and inverted

• + 80 cm from the mirror, virtual and erect

Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image? (Assume that the image is formed in front of the mirror.)

• + 40 cm from the mirror, real and inverted

• - 40 cm from the mirror, virtual and erect

• - 80 cm from the mirror, real and inverted

• + 80 cm from the mirror, virtual and erect

A virtual erect enlarged image is formed by a concave mirror of radius of curvature 30 cm. The object is placed at

• 13 cm

• 17 cm

• 21 cm

• 27 cm

• All the options are correct

An object of size 4cm is place 15 cm in front of a concave mirror of focal length 10 cm. Find the position and magnification of the image

• image is formed 30 cm in front of the mirror , m = -2

• image is formed 30 cm in front of the mirror , m = -8cm

• image is formed 30 cm behind the mirror , m = -2

• image is formed 30 cm behind the mirror , m = -8cm

An object of 2cm height is placed 16cm in front of a concave mirror. If the height of the image formed on a screen is 3 cm find the focal length of the mirror

• +9.6 cm

• - 9.6 cm

• - 24 cm

• +24 cm

An object of 2cm height is placed 32cm in front of a concave mirror. If the image formed on a screen is 3 cm find the focal length of the mirror

• +19.2 cm

• - 19.2 cm

• - 48 cm

• +48 cm

An object placed in front of a mirror of radius of curvature 30cm forms a real inverted image magnified three times. Find the position of the object and the image

• u = - 20 cm, v = - 60 cm

• u = - 60 cm, u = - 20 cm

• u = - 20 cm, v = + 60 cm

• u = - 60 cm, u = +20 cm

For an object placed 30 cm from a mirror, a real image is formed 60cm from the pole of the mirror. Find the position of the object to get an image at 40 cm from the pole of the mirror

• 20 cm

• 40 cm

• 10 cm

• 30 cm

For an object placed 30 cm from the pole of a mirror a virtual image is formed 60 cm from the pole of the mirror. Find the focal length of the mirror

• + 60 cm

• - 60 cm

• - 30 cm

• +30 cm