10th Class Science MCQs

Chapter 10 Reflection and Refraction

Topics: Properties of light, Object and Images Plane Mirror Sphercal Mirrors Focus and focal length of a concave Mirror and convex mirror Magnification Refrractive index lense formula Glass Slab.

2729

1. The power of a lens is +2 diopter. What will be its focal length?

$2 m$

$1 \mathrm{~m}$

$0.5 \mathrm{~m}$

$0.2 \mathrm{~m}$

2728

2. Image in a convex mirror will always be

real and upright

real and inverted

virtual and inverted

virtual and upright

2223

3. Which of the following materials cannot be used to make a lens?

Water

Glass

Plastic

Clay

2219

4. What is the formula for power of a lens?

P = 4f

P=2f

$P=\frac{1}{2f}$

$P=\frac{1}{f}$

2217

5. The magnification produced by a plane mirror is

-1

$<$1

$\mathrm{>}$1

2232

6. Angle of incidence is ............ to the angle of reflection.

larger

smaller

equal

none of these

2235

7. Image formed by a convex mirror is

erect, virtual and smaller in size

erect, real and large in size

inverted, virtual and equal in size

erect, virtual and smaller in size

2225

8. Which of the following lenses would you prefer to use while reading small letters found in dictionary?

A convex lens of focal length 50 cm.

A concave lens of focal length 50 cm.

A convex lens of focal length 5 cm.

A concave lens of focal length 5 cm.

2213

9. $\frac{{sin i\ }}{{sin r\ }}=n$ relation is

Snell's law

Newton's law

Mendel's law

Archimedes principle

2222

10. What is mirror formula?

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$

$\frac{1}{u}-\frac{1}{v}=\frac{1}{f}$

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

All of the above

2221

11. Which lens has negative power?

Convex lens

Concave lens

Both of these

None of the above

2228

12. The formula of magnification 'm' of a spherical mirror is

$\frac{v}{u}$

$\frac{-v}{u}$

$\frac{u}{v}$

$\frac{-u}{v}$

2215

13. Focal length of a concave mirror is

always positive

always negative

positive when image is real

negative when image is real

2212

14. Which mirror is used in a vehicle to see the rear view?

Plane

Convex

Concave

All of these

2211

15. Relation between focal length and radius of curvature is ......

f = 2R

$f=\frac{R}{2}$

$R=\frac{f}{2}$

$f=R$

Brief Notes: Chapter 10 - Lights Class 10

1. Light: Light is the radiant energy which produces in us the sensation of sight.

2. Rules of reflection of light:

(i) incident light, reflected light and perpendicular on the plane of reflection are in the same plane.

(ii) Angle of incidence 'i' is equal to the angle of reflection 'r'

3.Image Formed in Plane Mirror:

Image in a plane mirror is virtual and is at the same distance behind the mirror as that of the distance of object in front of mirror.

4. Cartesian sign conventions are used for spherical mirror and lens.

According to this convention -

The object is always placed towards left.
All distance are measured from the pole of the mirror. (from optical centre in case of lenses)
Distances of the left of the mirror or lens are taken as negative and distances towards the right are taken as positive.
The distances mesured above the principal axis are taken as positive and distances measured below the principal axis are taken as negative

Focal length and radius of curvature of a concave mirror are always negative while they are always positive for convex mirror. Similarly, the focal length of a concave lens is always taken as negative and focal length of convex lens is taken as positive.

5. In convex mirror, the image is always virtual, upright and simaller than the object. For a concave mirror the nature of image depends upon distance of object from the mirror.

6.Mirror Formula:

If object distance for a mirror is $u$, image distance is $\mathrm{v}$ and focal length is $\mathrm{f}$ then the morror formula is given as

$$\frac{1}{v}+ \frac{1}{u}=\frac{1}{f}$$

7.Magnification:

Ratio of height of image to the height of an object is called magnification.

8. Rules of refraction

(i) Incident ray, refracted ray and the perpendicular on the plane of refraction are in the same plane.
(ii) For a refracting medium the ratio of sine of angle of incidence 'i' and sine of angle of refraction ' $r$ ' is constant.

9.. When light rays travel through rarer medium to denser medium then at the plane of separation of both the mediums the rays bend towards the perpendicular after refraction. On the contrary when rays go from denser to rarer medium then after refraction the rays bend away from the perpendicular

10. Refractive Index

Ratio of speed of light in vacuum to the speed of light in a transparent medium is called refractive index of the transparent material.

11 Lense:

A refracting medium of two curved surfaces or one curved surface and one plane surface is called a lens.

12. Types of Lense

Lens are of two types.

(i) Convex lens or converging lens

(ii) Concave lens or diverging lens

13. Image formed in Lenses:

Image from a concave lens is always virtual, upright and smaller than the object. Image in a convex lens depends upon the distance of object from the lens.

14.Lens Formula:

If an object is at a distance $u$ from a lens, image is at distance $\mathrm{v}$ and focal length of lens is $\mathrm{f}$ then lens formula is given as

$$ \frac{1}{v}-\frac{1}{u}=\frac{1}{f} $$

15 Power of the Lens.

Reciprocal of the focal length of a lens is known as the power of the lens. Its unit is diopter.