Mirror Formula Examples

Q.

A square of side 3cm is placed at a distance of 25cm from a concave mirror

of focal length 10cm. The centre of the square is at the axis of the mirror and

the plane is normal to the axis. The area enclosed by the image of the square

is

1. 4cm²

2. 6cm²

3. 16cm²

4. 36cm²

Q. The image of an object placed on the principal axis of a concave mirror of focal length 12 cm is formed at a point which is 10 cm more distance from the mirror than the object. The magnification of the image is

1. $\frac{8}{3}$
2. $2.5$
3. $2$
4. $-1.5$

Q.

An object is placed at a distance of $20\text{cm}$ from the pole of a concave mirror whose focal length is $20\text{cm}$. Then image is formed at

1. $20\text{cm}$ from the pole of the mirror

2. $40\text{cm}$ from the pole of the mirror

3. at the pole of the mirror

4. at infinity

Q. A 3 cm tall object is placed at a distance of 7.5 cm from a convex mirror of focal length 6 cm. Find the location, size and nature of the image.

1. $\frac{10}{3}cm$ from the mirror on the side opposite to the object, virtual and erect,
2. $\frac{10}{3}cm$ fro the mirror on the same side as the object, virtual and erect.
   
3. $\frac{10}{3}cm$ from the mirror on the side opposite to the object, virtual and inverted.
4. $\frac{10}{3}cm$ from the mirror on the side opposite to the object, real and inverted.

Q. A candle flame 1.6 cm high is imaged in a ball bearing of diameter 0.4 cm. If the ball bearing is 20 cm away from the flame, find the location and the height of the image. (Assume the paraxial approximation to hold)

1. 1 mm behind the mirror and 0.08 mm high
2. 1 mm in front of the mirror and 0.08 mm high
3. 1 mm behind the mirror and 0.8 mm high
4. 10 mm in front of the mirror and 0.08 mm high

Q. A linear object is placed along the axis of a mirror as shown in figure. If $f$ is the focal length of the mirror, then the length of image is

1. $\frac{2f}{3}$
2. $f$
3. $\frac{f}{3}$
4. None of these

Q. The image of an object placed on the principal axis of a concave mirror of focal length 12 cm is formed at a point which is 10 cm more distance from the mirror than the object. The magnification of the image is

1. $\frac{8}{3}$
2. $2.5$
3. $2$
4. $-1.5$

Q. A concave mirror having a radius of curvature 40 cm is placed in front of an illuminated point source at a distance 30 cm from it. Find the location of the image.

1. 40 cm , behind the mirror
2. 60 cm, on the side of the object
3. 40 cm, on the side of the object
4. 60 cm, behind the mirror.

Q. The image of real object in a convexmirror is 4 cm from the mirror. If the radius of curvature of convex mirror is 24cm, the position of object is

1. 6 cm
2. 4 cm
3. 2 cm
4. 8 cm

Q. A man uses a concave mirror for shaving. He keeps his face at a distance of 25 cm from the mirror and gets an image which is 1.4 times enlarged. Find the focal length of the mirror. (The man does not see his face flipped upside down.)

1. 36.8 cm
   
2. 87.5 cm
   
3. 75.6 cm
   
4. 99.4 cm