Class 10 Science · Chapter 9

Light - Reflection and Refraction

409 Class 10 Science questions on Light - Reflection and Refraction from the NCERT textbook, NCERT Exemplar and CBSE board papers 2017–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 9 of 21

1. Q161 CBSE 2024
   A ray of light is ​incident on ​a ​plane mirror at an angle of incidence of $15^{\circ }$. ​The ​deviation in the ray produced ​by ​the mirror is :

   1. (a)$30^{\circ }$
   2. (b)$60^{\circ }$
   3. (c)$120^{\circ }$
   4. (d)$150^{\circ }$
   Show answer

   (d) $150^{\circ }$

   Step-by-step solution →
2. Q162 CBSE 2024
   For ​an object, ​a convex mirror always ​forms ​an ​image which ​is :

   1. (a)Virtual, erect and magnified
   2. (b)Virtual, erect and diminished
   3. (c)Virtual, inverted and diminished
   4. (d)Real, erect and diminished
   Show answer

   (b) Virtual, erect and diminished

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3. Q163 CBSE 2024
   Absolute refractive index of glass ​and ​water ​is $\frac{3}{2}$ and $\frac{4}{3}$ respectively. If ​the ​speed of ​light in glass is $2\times 10^8$ m/s, the speed of light in water is :

   1. (a)$\frac{9}{4}\times 10^8$ m/s
   2. (b)$\frac{5}{2}\times 10^8$ m/s
   3. (c)$\frac{7}{3}\times 10^8$ m/s
   4. (d)$\frac{16}{9}\times 10^8$ m/s
   Show answer

   (a) $\frac{9}{4}\times 10^8$ m/s

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4. Q164 CBSE 2024
   How ​will ​the image ​formed by a convex lens ​be affected, if the upper half ​of the ​lens ​is wrapped with a black paper ?

   1. (a)The size of the image formed will be one-half of the size of the image due to complete lens.
   2. (b)The image of upper half of the object will not be formed.
   3. (c)The brightness of the image will reduce.
   4. (d)The lower half of the inverted image will not be formed.
   Show answer

   (c) The brightness of the image will reduce.

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5. Q165 CBSE 2024
   At what distance from a convex lens ​should ​an object be placed to get an ​image of ​the same size as ​that ​of the object on a screen ​?

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

   (c) At twice the focal length of the lens.

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6. Q166 CBSE 2024
   The image formed by ​a concave mirror of focal length $50$ cm is ​real and of magnification $-1$. In this case the distance between ​the object ​from its ​own image is :

   1. (a)$50$ cm
   2. (b)$100$ cm
   3. (c)$200$ cm
   4. (d)Zero
   Show answer

   (d) Zero

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7. Q167 CBSE 2024
   The ​speed of light in vacuum is $3\times 10^8$ m/s. ​If the speed of light in a ​medium is $2.25\times 10^8$ ​m/s, the ​absolute refractive index ​of the ​medium is :

   1. (a)$\frac{7}{6}$
   2. (b)$\frac{5}{4}$
   3. (c)$\frac{4}{3}$
   4. (d)$\frac{3}{2}$
   Show answer

   (c) $\frac{4}{3}$

   Step-by-step solution →
8. Q168 CBSE 2024
   List four ​properties ​of the ​images ​formed ​by ​a plane ​mirror.
   Show answer

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

   Any four of these: (1) The image is virtual: it cannot be obtained on a screen. (2) It is erect. (3) It is of the same size as the object. (4) It is formed as far behind the mirror as the object is in front of it. (5) It is laterally inverted.

   Step-by-step solution →
9. Q169 CBSE 2024
   Write the definitions of the following terms in the ​context ​of a concave ​mirror:

   1. (i)​Pole
   2. (ii)Centre of curvature
   3. (iii)Radius ​of curvature
   4. (iv)Principal ​axis
   Show answer

   Pole is the mirror's centre, C is its sphere's centre, R equals PC, and the principal axis joins P and C.

   (i) Pole: The centre of the reflecting surface of the concave mirror is called its pole (P); it lies on the surface of the mirror. (ii) Centre of curvature: The reflecting surface of the mirror is a part of a sphere, and the centre of that sphere is the centre of curvature (C); it is not a part of the mirror and lies in front of a concave mirror. (iii) Radius of curvature: The radius of the sphere of which the reflecting surface forms a part is the radius of curvature (R); it equals the distance PC. (iv) Principal axis: The straight line passing through the pole and the centre of curvature is the principal axis; it is normal to the mirror at its pole.

   Step-by-step solution →
10. Q170 CBSE 2024
    A ray of light falls making an angle of incidence $\theta$ ​on ​the surface of ​a glass slab. Draw a ​labelled ray diagram to show its path. ​Also mark lateral ​displacement ​on it.
    Show answer

    The emergent ray is parallel to the incident ray, with $e=\theta$, and is shifted sideways by the lateral displacement.

    The incident ray meets the upper face at O at angle of incidence $\theta$ and bends towards the normal inside the glass (angle of refraction $r<\theta$). At the lower face O′ it bends away from the normal and leaves at angle of emergence $e=\theta$, so the emergent ray is parallel to the incident ray. The lateral displacement is the perpendicular distance between the emergent ray and the incident ray produced (dashed), marked on the diagram.

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11. Q171 CBSE 2024
    An object is placed ​at a distance of $10$ cm from a convex mirror of focal length $15$ ​cm. Find ​the ​position of ​the ​image ​formed ​by the mirror.
    Show answer

    $v=+6$ cm: the image is formed 6 cm behind the mirror, virtual, erect and diminished.

    $v=+6$ cm: the image is formed $6$ cm behind the mirror. It is virtual, erect and diminished ($m=+0.6$).

    Step-by-step solution →
12. Q172 CBSE 2024
    Draw ​a ​labelled ray ​diagram to show the formation of ​image ​due to a concave mirror when an object is placed ​between its ​pole ​and principal focus.
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    The image is formed behind the mirror and is virtual, erect and enlarged.

    Draw the concave mirror with P, F and C on the principal axis and place the object AB between P and F. From the top A draw (1) a ray along the line from C through A, which meets the mirror normally and is reflected back along the same path, and (2) a ray to the pole P, which is reflected at an equal angle on the other side of the principal axis (a ray parallel to the axis, reflected through F, may be used instead). The reflected rays diverge; produced backwards as dashed lines, they meet behind the mirror at A′. The image A′B′ is formed behind the mirror and is virtual, erect and enlarged. For example, with $f=-10$ cm and $u=-6$ cm the mirror formula gives $v=+15$ cm and $m=+2.5$.

    Step-by-step solution →
13. Q173 CBSE 2024
    State ​two ​laws ​of ​refraction ​of light.
    Show answer

    The incident ray, refracted ray and normal lie in one plane, and $\frac{\sin i}{\sin r}$ is constant (Snell's law).

    (1) The incident ray, the refracted ray and the normal to the interface of the two transparent media at the point of incidence all lie in the same plane. (2) The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for light of a given colour and for the given pair of media, $\frac{\sin i}{\sin r}=\text{constant}$ (Snell's law of refraction); this constant is the refractive index of the second medium with respect to the first.

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14. Q174 CBSE 2024
    Define the ​term absolute refractive index of a medium. A ​ray ​of light enters from vacuum to ​glass ​of absolute refractive index $1.5$. Find the speed of light in ​glass. The speed of light in vacuum is $3\times 10^8$ ​m/s.
    Show answer

    The absolute refractive index is $n=\frac{c}{v}$ (vacuum speed over medium speed); light travels at $2\times 10^8$ m/s in glass.

    The absolute refractive index of a medium is the ratio of the speed of light in vacuum to the speed of light in that medium, $n_m=\frac{c}{v}$. For glass, $v=\frac{c}{n_g}=\frac{3\times 10^8}{1.5}=2\times 10^8$ m/s.

    Step-by-step solution →
15. Q175 CBSE 2024
    The heat ​produced ​at a point due to concentration of sunlight by a convex ​lens ​burns a paper.

    1. (a)Explain why it ​happens.
    2. (b)Name the term (in the context of the lens ​used) given to the point at ​which the paper starts burning. What does the bright spot formed on the ​paper represent ?
    Show answer

    The lens focuses parallel sunlight at its principal focus; the bright spot there is the real image of the Sun.

    (a) The Sun is very far away, so its rays reach the lens parallel to one another. The convex lens is a converging lens: it refracts these parallel rays so that they meet at one point. All the light energy falling on the lens is concentrated into a tiny spot, and the heat produced there raises the temperature of the paper until it burns. (b) The point is the principal focus ($F$) of the convex lens. The bright spot on the paper is the real image of the Sun formed by the lens.

    Step-by-step solution →
16. Q176 CBSE 2024
    Define power ​of a lens. Find ​power of ​a lens whose focal length is ​50 ​cm.
    Show answer

    Power is the reciprocal of focal length in metres, $P=\frac{1}{f}$, measured in dioptres; the lens has $P=+2$ D.

    Power of a lens is the reciprocal of its focal length expressed in metres, $P=\frac{1}{f}$; it measures the degree of convergence or divergence of light that the lens produces, and its SI unit is the dioptre (D), the power of a lens of focal length 1 m. For $f=50$ cm $=0.5$ m: $P=\frac{1}{0.5\text{m}}=+2$ D, a converging (convex) lens.

    Step-by-step solution →
17. Q177 CBSE 2024
    “The linear ​magnification produced by ​a ​spherical mirror ​is $+3$.” Based on this statement answer the following questions :

    1. (a)What is the type of mirror ?
    2. (b)Where is the object located ​?
    3. (c)List two properties of the image formed (other ​than ​the size/magnification).
    Show answer

    A concave mirror, with the object between P and F; the image is virtual and erect, formed behind the mirror.

    (a) The mirror is a concave mirror. (b) The object is between the pole P and the principal focus F of the mirror, that is, closer to the mirror than F. (c) The image is virtual and erect; it is formed behind the mirror.

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18. Q178 CBSE 2024
    An object is ​placed ​in front of a concave mirror of focal length 12 ​cm. If distance of the object ​from the pole of the mirror is 8 cm, then use mirror formula to determine the position of ​the image formed. Draw a ​labelled ray diagram to justify your answer in this case.
    Show answer

    The image is 24 cm behind the mirror, virtual, erect and three times the size of the object.

    The image is formed 24 cm behind the mirror ($v=+24$ cm). It is virtual and erect, and three times the size of the object ($m=+3$). Ray diagram: a ray from the top of the object parallel to the principal axis is reflected through F, and a ray along the line from C through the top of the object is reflected back along itself. The two reflected rays diverge, and their backward extensions meet 24 cm behind the mirror, where the erect, enlarged image is seen.

    Step-by-step solution →
19. Q179 CBSE 2024
    A ​student ​has focussed the image of an object of ​height 5 cm on a screen ​using a convex lens of focal length 20 cm. If the object distance ​is 30 cm ​find, using lens formula, the

    1. (i)image distance and
    2. (ii)​height of the image produced.
    Show answer

    $v=+60$ cm and $h^{\prime }=-10$ cm: the image is 10 cm tall and inverted, formed 60 cm from the lens.

    (i) Image distance $v=+60$ cm: the image is formed $60$ cm from the lens, on the side opposite to the object, where the screen is. (ii) Height of the image $h^{\prime }=-10$ cm: the image is $10$ cm tall and inverted (magnification $m=-2$).

    Step-by-step solution →
20. Q180 CBSE 2024
    1. (i)The image of ​an object ​formed by a mirror is real, inverted and ​is of magnification $-1$. If the image is at a distance of 30 ​cm from ​the mirror, where is the object placed ? Give reason to justify ​your answer.
    2. (ii)Where would the image be if the object is moved 15 cm towards the mirror ​? Draw ray diagram for the new position of ​the object to justify your answer.
    Show answer

    The object is at C, 30 cm from the mirror; moved 15 cm closer, it is at F and the image forms at infinity.

    (i) The object is placed 30 cm in front of the mirror ($u=-30$ cm), at its centre of curvature C. Reason: only a concave mirror forms a real, inverted image, and $m=-\frac{v}{u}=-1$ means $u=v=-30$ cm; then $\frac{1}{f}=-\frac{1}{30}-\frac{1}{30}=-\frac{1}{15}$, so $f=-15$ cm and $R=30$ cm. A concave mirror forms a real, inverted image of the same size only when the object is at C, and the image then forms at C too. (ii) Moving the object 15 cm towards the mirror puts it at $u=-15$ cm, the principal focus F. Then $\frac{1}{v}=-\frac{1}{15}+\frac{1}{15}=0$, so the image is formed at infinity: real, inverted and highly enlarged. In the ray diagram the two reflected rays leave the mirror parallel to each other.

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