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.


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1. No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be?

2234

2. SI unit of power of a lens is

2222

3. What is mirror formula?

2731

4. To get a real image of the same size of object, where shall the object be placed before a convex lens of focal length $15 \mathrm{~cm}$ ?

2228

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

2721

6. Which mirror will show a wide area view

2227

7. The formula of magnification 'm' of a lens is .......

2723

8. Which mirror will show a wide area view

2229

9. The colour of danger signal is ......

2211

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

2219

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

2727

12. Focal length of a plane mirror is

2236

13. Shaving mirrors are

2225

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

2215

15. Focal length of a concave mirror is

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.