Class 10 Science · Chapter 9

Light - Reflection and Refraction

194 Class 10 Science questions on Light - Reflection and Refraction from the NCERT textbook, NCERT Exemplar and CBSE board papers 2023–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 1 of 10

1. Q1 NCERT · Exercises
   Which one ​of the following materials cannot ​be ​used to ​make ​a lens?

   1. (a)Water
   2. (b)Glass
   3. (c)Plastic
   4. (d)Clay
   Show answer

   (d) Clay

   Step-by-step solution →
2. Q2 NCERT · Intext Questions (Page 142)
   Define ​the ​principal ​focus ​of a ​concave ​mirror.
   Show answer

   It is the point on the principal axis where rays parallel to the axis actually meet after reflection from the concave mirror.

   The principal focus of a concave mirror is the point on its principal axis at which rays of light coming parallel to the principal axis actually meet after being reflected from the mirror. It is denoted by $F$, it lies in front of the mirror, and the distance of $F$ from the pole $P$ is the focal length $f$, equal to half the radius of curvature ($f=R/2$).

   Step-by-step solution →
3. Q3 NCERT · Exercises
   The image formed by a concave mirror is ​observed ​to be virtual, erect and ​larger ​than ​the object. Where should ​be the position of the object?

   1. (a)Between the principal focus and the centre of curvature
   2. (b)At the centre of curvature
   3. (c)Beyond the centre of curvature
   4. (d)Between the pole of the mirror and its principal focus.
   Show answer

   (d) Between the pole of the mirror and its principal focus.

   Step-by-step solution →
4. Q4 NCERT · Intext Questions (Page 142)
   The ​radius ​of ​curvature of ​a spherical mirror is $20$ ​cm. What is ​its focal length?
   Show answer

   The focal length is $10\text{cm}$, half the radius of curvature; its sign is negative for a concave and positive for a convex mirror.

   The focal length is $10$ cm, because $f=R/2=20/2$. The stem does not say whether the mirror is concave or convex, so only the size is fixed: on the New Cartesian sign convention a concave mirror of this radius has $f=-10$ cm and a convex one has $f=+10$ cm.

   Step-by-step solution →
5. Q5 NCERT · Exercises
   Where should an object be placed in front of ​a convex ​lens to ​get a ​real image of the ​size ​of the ​object?

   1. (a)At the principal focus of the lens
   2. (b)At twice the focal length
   3. (c)At infinity
   4. (d)Between the optical centre of the lens and its principal focus.
   Show answer

   (b) At twice the focal length

   Step-by-step solution →
6. Q6 NCERT · Intext Questions (Page 142)
   Name a ​mirror ​that ​can give an erect ​and enlarged image ​of ​an object.
   Show answer

   A concave mirror, with the object between its pole and focus, gives a virtual, erect and enlarged image.

   A concave mirror, with the object placed between the pole $P$ of the mirror and its principal focus $F$ — that is, nearer to the mirror than one focal length. The image is then formed behind the mirror, and it is virtual, erect and enlarged. A plane mirror can only give an image of the same size and a convex mirror only a diminished one, so neither of those will do.

   Step-by-step solution →
7. Q7 NCERT · Exercises
   A spherical ​mirror and ​a thin ​spherical lens ​have ​each ​a ​focal length of $-15$ cm. The mirror and the ​lens are likely to be

   1. (a)both concave.
   2. (b)both convex.
   3. (c)the mirror is concave and the lens is convex.
   4. (d)the mirror is convex, but the lens is concave.
   Show answer

   (a) both concave.

   Step-by-step solution →
8. Q8 NCERT · Intext Questions (Page 142)
   Why do we ​prefer ​a ​convex mirror as a rear-view ​mirror ​in ​vehicles?
   Show answer

   It always gives an erect, diminished image and a wider field of view than a plane mirror, so the driver sees more traffic behind.

   Because a convex mirror does two things a driver needs at once. First, whatever the distance of the object, it always forms a virtual, erect and diminished image, so the traffic behind is seen the right way up and never inverts. Second, its reflecting surface curves outwards, which gives it a much wider field of view than a plane mirror of the same size, so the driver sees a far larger stretch of the road behind in a small mirror. The price is that the image is diminished, which is why such mirrors warn that objects are closer than they appear.

   Step-by-step solution →
9. Q9 NCERT · Exercises
   No matter how ​far you stand ​from a ​mirror, your image appears ​erect. The ​mirror is ​likely to be

   1. (a)only plane.
   2. (b)only concave.
   3. (c)only convex.
   4. (d)either plane or convex.
   Show answer

   (d) either plane or convex.

   Step-by-step solution →
10. Q10 NCERT · Exercises
    Which of the ​following ​lenses would you ​prefer ​to ​use ​while reading small letters ​found ​in a dictionary?

    1. (a)A convex lens of focal length $50$ cm.
    2. (b)A concave lens of focal length $50$ cm.
    3. (c)A convex lens of focal length $5$ cm.
    4. (d)A concave lens of focal length $5$ cm.
    Show answer

    (c) A convex lens of focal length $5$ cm.

    Step-by-step solution →
11. Q11 NCERT · Exercises
    We wish to obtain ​an ​erect image ​of an object, using a concave mirror of focal ​length $15$ cm. What should be the range ​of distance of ​the object from the mirror? What is the nature of ​the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation ​in this case.
    Show answer

    The object must be nearer than 15 cm (between pole and focus); the image is virtual, erect and larger than the object.

    The object must be placed at a distance of less than 15 cm from the mirror, that is anywhere between the pole and the principal focus. The image is then virtual and erect, and it is formed behind the mirror. It is larger than the object. For example, with the object at 10 cm the mirror formula gives $v=+30$ cm and $m=-\frac{v}{u}=+3$, so the image stands 30 cm behind the mirror, upright and three times as tall as the object.

    Step-by-step solution →
12. Q12 NCERT · Exercises
    Name the type ​of mirror ​used in the following situations.

    1. (a)Headlights of a car.
    2. (b)Side/rear-view ​mirror ​of a vehicle.
    3. (c)​Solar furnace. Support ​your ​answer with reason.
    Show answer

    Car headlights and solar furnaces use concave mirrors; rear-view mirrors use convex mirrors for a wider field of view.

    (a) Concave mirror. The bulb is placed at its principal focus, so the light reflected from the mirror leaves as a parallel beam that travels far down the road without spreading. (b) Convex mirror. It always forms a virtual, erect and diminished image, whatever the distance of the vehicle behind, and it has a much wider field of view than a plane mirror of the same size, so the driver sees more of the traffic behind. (c) Concave mirror. A large concave mirror reflects the parallel rays of sunlight through its focus, concentrating the energy collected over its whole surface onto a small target placed there, which reaches a very high temperature.

    Step-by-step solution →
13. Q13 NCERT · Exercises
    One-half ​of a convex lens is ​covered with a black paper. Will this lens ​produce ​a complete image ​of the object? Verify your ​answer experimentally. Explain your ​observations.
    Show answer

    Yes, it still forms a complete image of the same size and position, only fainter, since the remaining rays still reach every image point.

    Yes. The lens still produces a complete image of the object, in the same position and of the same size as before, but the image is fainter. Light from every point of the object falls on the whole face of the lens, and every one of those rays is refracted to the same image point, so covering half the lens removes some of the rays that build each image point but never removes an image point itself. Experimentally, a lighted candle and a screen give a sharp inverted image; covering the upper half of the lens, and then the lower half instead, leaves the same complete image on the screen both times, only dimmer. The brightness falls to about half because only half the area of the lens is now collecting light, while the position and size are fixed by $\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$ and $m=\frac{v}{u}$, in which the exposed area does not appear.

    Step-by-step solution →
14. Q14 NCERT · Exercises
    An object $5$ cm in ​length is held $25$ ​cm ​away from a ​converging lens of focal length $10$ cm. Draw the ray ​diagram and find the ​position, size ​and the ​nature of the image formed.
    Show answer

    $v=+16.7$ cm: the image is real and inverted, 3.3 cm long and 16.7 cm from the lens on the side opposite the object.

    The image is formed $16.7$ cm from the lens, on the side opposite the object. It is $3.3$ cm in size — reduced to two-thirds of the object — and it is real and inverted.

    Step-by-step solution →
15. Q15 NCERT · Exercises
    A concave lens of focal length $15$ cm forms an image $10$ ​cm from ​the lens. How far ​is ​the ​object placed from the ​lens? Draw ​the ray diagram.
    Show answer

    The object is 30 cm from the lens on the same side as the image ($u=-30$ cm); the image is virtual, erect and diminished.

    The object is placed $30$ cm from the lens, on the same side as the image (in the sign convention, $u=-30$ cm). The image is virtual, erect and one-third the size of the object.

    Step-by-step solution →
16. Q16 NCERT · Exercises
    An object ​is ​placed at a distance of $10$ cm from ​a ​convex ​mirror of focal length $15$ cm. Find the position ​and ​nature of the image.
    Show answer

    $v=+6.0$ cm: the image is 6.0 cm behind the mirror, virtual, erect and diminished ($m=+0.6$).

    The image is formed $6.0$ cm behind the mirror. It is virtual and erect, and diminished to $0.6$ times the size of the object.

    Step-by-step solution →
17. Q17 NCERT · Exercises
    The ​magnification ​produced by a ​plane ​mirror is $+1$. ​What does ​this mean?
    Show answer

    The image is the same size as the object, virtual and erect, and as far behind the mirror as the object is in front.

    $m=1$ indicates that the image formed by a plane mirror is exactly the same size as the object; the positive sign indicates that the image is virtual and erect. Since $m=-v/u$, it also follows that $v=-u$, so the image stands as far behind the mirror as the object stands in front of it.

    Step-by-step solution →
18. Q18 NCERT · Exercises
    An ​object $5.0$ ​cm in length is placed at ​a distance of $20$ cm ​in front of a convex mirror ​of ​radius of curvature $30$ cm. Find the position of ​the image, its nature and size.
    Show answer

    The image is $8.6\text{cm}$ behind the mirror, virtual and erect, and reduced to $2.2\text{cm}$ ($m=+0.43$).

    The image is formed $8.6$ cm behind the mirror. It is virtual and erect, and its size is $2.2$ cm — reduced, since the magnification is $+0.43$.

    Step-by-step solution →
19. Q19 NCERT · Exercises
    An object of ​size $7.0$ cm is placed at $27$ cm in ​front of a ​concave mirror of focal length $18$ cm. At what distance from the ​mirror ​should ​a screen be placed, so ​that a ​sharp focussed image can be obtained? Find the size and the nature of the image.
    Show answer

    The screen is 54 cm from the mirror on the object side; the image is real, inverted, magnified two times, 14 cm tall.

    The screen should be placed $54$ cm from the mirror, on the object side — the same side as the object (in the sign convention, $v=-54$ cm). The image obtained there is $14$ cm in size — magnified two times — and it is real and inverted.

    Step-by-step solution →
20. Q20 NCERT · Exercises
    Find ​the focal ​length of a lens of ​power $-2.0$ D. ​What ​type of ​lens is ​this?
    Show answer

    $f=-0.50$ m (that is $-50$ cm); the negative sign shows a concave, diverging lens.

    The focal length is $-0.50$ m, that is $-50$ cm. The negative sign shows that this is a concave lens — a diverging lens.

    Step-by-step solution →