Mirror Formula and Magnification

Q.

Mirror magnification formula

Q.

Relate the image distance ($v$), object distance ($u$) , image height ($h^{{}^{\prime }}$) and object height ($h$) to the formula of magnification $\left(M\right)$ for a mirror.

1. $M=\frac{h}{h^{\prime }}$ = $\frac{v}{u}$

2. $M=\frac{h^{\prime }}{h}$ = $\frac{-u}{v}$

3. $M=\frac{h^{\prime }}{h}$ = $\frac{-v}{u}$

4. $M=\frac{h^{\prime }}{h}$ = $\frac{u}{v}$

Q.

An object 5 cm high is placed at a distance of 60 cm in front of a concave mirror of focal length 10 cm. Find (i) the position and (ii) size, of the image.

Q.

An object of height 7 cm is kept at a distance of 25 CM in front of a concave mirror . The focal length of the mirror is 15 cm. At what distance from the mirror should a screen be kept so as to get a clear image? What will be the size and nature of image

Q.

An object is placed at 4 cm distance in front of a concave mirror of radius of curvature 24 cm. Find the position of image. Is the image magnified ?

Q. Object is placed on the principal axis of a concave mirror. Its real image is formed at a point which is 10 cm more distant from the mirror than the object. If focal length of mirror 12 cm. The magnification of the image is:

1. 1.5
2. 1
3. 2
4. 2.5

Q.

A point light source is kept in front of a convex mirror at a distance of 40 cm. The focul length of the mirror is 40 cm. Find the position of image.

Q.

The image formed by a convex mirror is of size one-third the size of object. How are u and v related ?

Q.

The erect image formed by a concave mirror is of size double the size of object. How are u and v related ?

Q. When an object of height 1 cm is kept at a distance 4 cm from a concave mirror , its erect image of height 1.5 cm is formed at a distance 6 cm behind the mirror .Find the focal length of mirror?

Q.

A convergent beam is incident on concave mirror, what will be the nature of image?

1. Real and erect
2. Virtual and erect
3. Real and inverted
4. Virtual and inverted

Q. An object 5 cm high is placed at a distance 60 cm in front of a concave mirror of a focal length 10 cm.find
the position and the size?

Q.

Consider the situatuion shown in figure. A plane mirror is fixed at a height h above the bottom of a beaker containing water (refractive index $\mu$ ) up to a height d. Find the position of the image of the bottom formed by the mirror.

1. $h-d+\frac{d}{\mu }.$

2. $h+d+\frac{d}{\mu }.$

3. $h-d-\frac{d}{\mu }.$

4. $d+\frac{d}{\mu }.$

Q. The radius of curvature of a convex mirror used on a moving automobile is $2m$. A truck is behind it at a constant distance of $3.5m$. Calculate the position, nature and size of the image relative to the size of the truck.

Q.

If object is placed at 60 cm before the concave mirror. The object moves with velocity 20 cm/sec towards the mirror. The magnification is -1/2 at initial position. And if magnification after 1 sec is – 1 find out the average velocity of the image for above 1 sec period.

1. 10 cm/sec

2. 20 cm/sec

3. 15 cm/sec

4. 5 cm/sec

Q. A motor car is fitted with a rear view mirror of focal length 20 cm . A second motor car 2 m broads and 21.6 m high is 6 m away from first car. Find the position of second car as seen in the mirror of the first car .

Q. The real image of an extended object, placed in front of a concave mirror, is formed at a distance of 40 cm from the object. If the image is 3 times bigger than the object, the magnitude of focal length of the mirror is ?

1. 15 cm
2. 10 cm
3. 20 cm
4. 5 cm

Q. The linear magnification for a mirror is the ratio of the size of the image to the size of the object, and is denoted by $m$. Then we may write: (symbols have their usual meanings)

1. $f=\frac{1+m}{mu}$
2. $f=mu$
3. None of these
4. $f=\frac{mu}{1+m}$

Q. An object of height $1.2m$ is placed before a concave mirror of focal length $20cm$ so that a real image is formed at a distance of $60cm$ from it. Find the position of an object. What will be the height of the image formed?

Q. A concave mirror forms a virtual image of size twice that of the object placed at a distance 5 cm from it. Find:
(a) the focal length of the mirror(b) position of image.

Q. A concave mirror produces a real image twice the size of the object when placed at a distance of 22.5 cm from it. Where should be object be placed so that the size of the image becomes three times that of the object?

1. 20 cm
2. 22.5 cm
3. 24 cm
4. 30.4 cm

Q. A $1cm$ height needle is placed at a distance of $0.1m$ from a convex mirror of focal length $0.05m$, then size of the image is

1. $0.5cm$
2. $0.66cm$
3. $0.33cm$
4. $1cm$

Q.

The magnification in a spherical mirror is:

1. Negative of the ratio of image height to the object height

2. Negative of the ratio of the image distance to the object distance

3. The ratio of image distance to the object distance

4. Negative of the ratio of the object distance to the image distance

Q. When an object is at distances of $u_1$ and $u_2$ from the poles of a concave mirror, images of the same size are formed. The focal length of the mirror is:

1. $|u_1+u_2|$
2. $|u_1-u_2|$
3. $|\frac{u_1+u_2}{2}|$
4. $|\frac{u_1-u_2}{2}|$

Q. For an inverted image, the height is taken as

1. negative
2. undefined
3. zero
4. positive

Q. For an inverted image, the height is taken as

1. undefined
2. zero
3. positive
4. negative

Q. What is the nature of the image formed by a concave mirror if the magnification produced by the mirror is +3?[1 marks]

Q. An observer whose least distance of distinct vision is 'd', views his own face in a convex mirror or radius or curvature 'r'. The magnification produced cannot exceed $\frac{kr}{d+\sqrt{d^2+r^2}}$. Find $k$

1. 1
2. 2
3. 3
4. 4

Q. A cube of side length $1mm$ is placed on the axis of a concave mirror at a distance of $45cm$ from the pole, as shown in the figure. One edge of the cube is parallel to the axis. The focal length of the mirror is $30cm$. Find the approximate volume of the image.

Q. The image formed by a concave mirror of focal length $6cm$ is $3$ times of the object, then the distance of the object from the mirror is

1. $-4cm$
2. $8cm$
3. $6cm$
4. $12cm$