Relationship between Focus and Radius of Curvature

Q.

Find the focal length of a convex mirror whose radius of curvature is $32cm$.

Q.

What is the relation between the focal length and radius of curvature of a spherical mirror (concave mirror or convex mirror) ? Calculate the focal length of a spherical mirror whose radius of curvature is 25 cm.

Q.

The focal length of a spherical mirror of radius of curvature 30 cm is : (a) 10 cm (b) 15 cm (c) 20 cm (d) 30 cm

Q.

Question 2
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?

Q.

Find the focal length of a concave mirror whose radius of curvature is 32 cm.

Q.

If the radius of curvature $\left(R\right)$ of a convex mirror is $30cm$. What is its focal length?

1. $30cm$

2. $60cm$

3. $10cm$

4. $15cm$

Q. Focal length of a convex mirror is $15\text{cm}$. Its radius of curvature is

Q.

If the focal length of a convex mirror is 25 cm, what is its radius of curvature ?

Q.

If the focal length of a spherical mirror is 12.5 cm, its radius of curvature will be : (a) 25 cm (b) 15 cm (c) 20 cm (d) 35 cm

Q.

The distance between pole of the mirror and the centre of curvature is

1. Object distance

2. Radius of curvature

3. Aperture

4. Focal length

Q.

If R is the radius of curvature of a spherical mirror and f is its focal length, then : (a) R = f (b) R=2f (c) R=$\frac{f}{2}$ (d) R=3f

Q. The radius of curvature of a concave mirror is $\text{12 cm}$. If I want to capture the image of the sun, at what distance from the pole of the mirror would an image be formed?

1. 6

Q.

If the focal length of a spherical mirror is 12.5 less cm, what will be its radius of curvature?

Q. A concave mirror is a converging mirror, and a convex mirror is a diverging mirror.

1. False
2. True

Q.

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

Q.

The name and radius of curvature of a spherical mirror whose focal length is +2 cm is

1. +4 cm; Convex

2. -4 cm ; Concave

3. -4 cm; convex

4. +4 cm; concave

Q. ___ is the linear distance between the pole and principal axis.

Q.

If focal length of a spherical mirror is 20 cm, then its radius of curvature is equal to

1. 10 cm

2. 20cm

3. 5cm

4. 40cm

Q.

The focal length of a mirror is the

1. Distance of the focus from the centre

2. Half the radius of curvature.

3. Distance of the focus from the pole

4. Distance of the centre from the pole

Q.

If the radius of curvature of a spherical mirror is 34.52 cm, then the focal length of that spherical mirror is

1. 17.26 cm

2. -34.52 cm

3. 34.52 cm

4. 69.04 cm

Q. In a car, a rearview mirror having a radius of curvature of 20 m forms a virtual image of a bus 5 m behind the mirror. What is the actual distance of the bus from the car?

[0.8 mark]

1. 10 m
2. 20 m
3. 5 m
4. 5/3 m

Q. a) What is the relation between focal length & radius of curvature? Calculate the focal length of convex lens having radius of curvature as 2 m. [2 Marks]

b) A candle, 4 cm in size is placed at 25 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and size of the image.
[3 Marks]

Q. When the wavelength of the light used is increased the focal length of a spherical mirror

1. Remains same
2. Increases
3. Decreases to half its value
4. Decreases slightly

Q. What is the relation between the focal length and radius of curvature of a spherical mirror (concave mirror of convex mirror)? Calculate the focal length of a spherical mirror whose radius of curvature is 25 cm.

Q. A concave mirror is half dipped in water. Focal length of portion of mirror is the air is $f_1$ and focal length of mirror in water is $f_2$, then (Take refractive index of water $=\frac{4}{3}$)

1. $f_1<f_2$
2. $f_1>f_2$
3. $f_1\ge \frac{4}{3}{f}_2$
4. $f_1=f_2$

Q. State whether true or false :

1. True
2. False

Q. A concave mirror of focal length $f$ and diameter $d(d<<f)$ is kept horizontally and filled with water. Rays of light parallel to the mirror axis are incident on it. After reflection, the rays will focus close to

1. 1.33f
2. f
3. 0.25f
4. 0.75f

Q. The radius of curvature of a concave mirror is $40cm$. Determine its focal length.

Q.

In the above figure, the distance between the point P and point F is

1. Radius of curvature

2. Focal length

3. Aperture

4. Centre of curvature

Q.

Question 2
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?