Class 10 Science · Chapter 10

The Human Eye and the Colourful World

281 Class 10 Science questions on The Human Eye and the Colourful World 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 15

1. Q161 CBSE 2024
   1. (a)Study the following ray diagram ​and ​name the angles given ​below : $\angle \mathrm{PEN}$, $\angle {\mathrm{FEN}}^{\prime }$, $\angle \mathrm{SFM}$ ​and $\angle \mathrm{FGH}$
   2. (b)In this ​diagram, if $\frac{\sin \angle \mathrm{PEN}}{\sin \angle {\mathrm{FEN}}^{\prime }}=\frac{3}{2}$, ​what is the ​value of $\frac{\sin \angle \mathrm{SFM}}{\sin \angle \mathrm{EFM}}$ ? Give reason ​to justify your answer.

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   The angles are incidence, refraction, emergence and deviation, and the ratio is $\frac{3}{2}$ because both faces involve the same two media.

   (a) $\angle \mathrm{PEN}$ is the angle of incidence ($i$), $\angle {\mathrm{FEN}}^{\prime }$ the angle of refraction ($r$), $\angle \mathrm{SFM}$ the angle of emergence ($e$) and $\angle \mathrm{FGH}$ the angle of deviation ($D$). (b) The value is $\frac{3}{2}$. The given ratio is the refractive index of glass with respect to air, $n_{ga}=\frac{3}{2}$. At F the light passes from glass into air, with $\angle {\mathrm{EFM}}^{\prime }$ the angle in glass and $\angle \mathrm{SFM}$ the angle in air, so Snell’s law gives $\frac{\sin \angle {\mathrm{EFM}}^{\prime }}{\sin \angle \mathrm{SFM}}=\frac{1}{n_{ga}}=\frac{2}{3}$, that is $\frac{\sin \angle \mathrm{SFM}}{\sin \angle {\mathrm{EFM}}^{\prime }}=\frac{3}{2}$: the same two media give the same ratio at both faces. The printed $\angle \mathrm{EFM}$ stands for $\angle {\mathrm{EFM}}^{\prime }$; as M, F and M′ are collinear the two angles have equal sines, so the value is $\frac{3}{2}$ either way.

   Step-by-step solution →
2. Q162 CBSE 2023
   The ​change ​in the focal length of an eye ​lens in ​human beings is ​caused ​by ​the action ​of

   1. (a)optic nerves
   2. (b)ciliary muscles
   3. (c)retina
   4. (d)cornea
   Show answer

   (b) ciliary muscles

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3. Q163 CBSE 2023
   In the following diagram showing ​dispersion of white light ​by a glass ​prism, the colours ​'P' and ​'Q' respectively are ​–

   1. (a)Red and Violet
   2. (b)Violet and Red
   3. (c)Red and Blue
   4. (d)Orange and Green
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   (b) Violet and Red

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4. Q164 CBSE 2023
   When a narrow beam of white light passes ​through ​a glass prism it splits into ​its ​component colours ? This ​phenomenon ​is called :

   1. (a)Diffusion of light
   2. (b)Total reflection of light
   3. (c)Scattering of light
   4. (d)Dispersion of light
   Show answer

   (d) Dispersion of light

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5. Q165 CBSE 2023
   The phenomena ​of ​light involved ​in ​the ​formation of ​rainbow ​are

   1. (a)Refraction, dispersion and scattering.
   2. (b)Refraction, reflection and dispersion.
   3. (c)Refraction, dispersion and internal reflection.
   4. (d)Reflection, dispersion and total internal reflection.
   Show answer

   (c) Refraction, dispersion and internal reflection.

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6. Q166 CBSE 2023
   In human eye ​the part which allows ​light to enter ​into the ​eye ​is ​–

   1. (a)Retina
   2. (b)Pupil
   3. (c)Eye lens
   4. (d)Cornea
   Show answer

   (b) Pupil

   Step-by-step solution →
7. Q167 CBSE 2023
   Two ​statements are given — ​one labelled as Assertion (A) ​and the other labelled as Reason (R). Select the ​correct ​answer to this question from the codes ​(a), (b), ​(c) and (d) as given ​below.

   Assertion (A): A person suffering from myopia cannot see the distant objects clearly.

   Reason (R): A converging lens is used for the correction of myopic eye as it can form real as well as virtual images of the objects placed in front of it.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
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   (c) Assertion (A) is true, but Reason (R) is false.

   Step-by-step solution →
8. Q168 CBSE 2023
   Two statements are ​given — one ​labelled ​as Assertion (A) and the ​other labelled as ​Reason (R). ​Select the correct answer to ​this question from the codes (a), (b), (c) and (d) as given below.

   Assertion (A): The angle through which a ray of light bends on passing through a prism is called the angle of deviation.

   Reason (R): The peculiar shape of a prism makes the emergent ray bend at an angle to the direction of the incident ray.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

   Step-by-step solution →
9. Q169 CBSE 2023
   Two statements ​are ​given — ​one ​labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to this question ​from the ​codes (a), (b), (c) and (d) as given below.

   Assertion (A): A rainbow is an artificial spectrum of white light appearing in the sky after a rain shower.

   Reason (R): The water droplets act like small prisms.

   1. (a)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
   2. (b)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
   3. (c)Assertion (A) is true, but Reason (R) is false.
   4. (d)Assertion (A) is false, but Reason (R) is true.
   Show answer

   (d) Assertion (A) is false, but Reason (R) is true.

   Step-by-step solution →
10. Q170 CBSE 2023
    When and ​where does a rainbow appear ​in the sky ? ​Draw ​a ​labelled ray diagram to ​show its formation.
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    A rainbow appears after rain in the sky opposite the Sun, formed by refraction, dispersion and internal reflection in raindrops.

    A rainbow appears after a rain shower, while tiny water droplets are still suspended in the air and the Sun is shining (it is also seen in the spray of a waterfall or a fountain). It appears in the part of the sky **opposite** the Sun, so the observer must stand with the back towards the Sun. Formation: sunlight entering a spherical raindrop is refracted and dispersed into its colours, the dispersed rays are reflected internally at the far surface of the drop, and they are refracted again as they leave it. Red emerges at about $42^{\circ }$ and violet at about $40^{\circ }$ to the incoming sunlight, so the arc carries red on the outside and violet on the inside.

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11. Q171 CBSE 2023
    What is scattering of light ? ​Why does the clear ​sky ​appear ​blue ​?
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    Scattering spreads light in all directions; air molecules scatter blue light most strongly, so the clear sky looks blue.

    Scattering of light is the phenomenon in which light falling on very fine particles of a medium is thrown back, or spread out, in all directions instead of travelling on in a straight line. The colour of the scattered light depends on the size of the scattering particle: very fine particles scatter mainly the shorter wavelengths. The molecules of the air are much smaller than the wavelength of visible light, so they scatter blue light, which has a short wavelength, far more strongly than red light, which has a long wavelength. This scattered blue light reaches our eyes from every direction, and so the clear sky appears blue.

    Step-by-step solution →
12. Q172 CBSE 2023
    Observe ​the following diagram showing ​an image ​formation in an eye :

    1. (a)Identify the defect of vision shown in the figure.
    2. (b)List its two causes and ​suggest a ​suitable corrective lens ​to ​overcome ​this defect.

    Show answer

    The defect is hypermetropia, with the image behind the retina, corrected by a convex lens.

    (a) The defect is hypermetropia, that is far-sightedness or long-sightedness: the image is formed behind the retina. (b) Two causes: (1) the focal length of the eye lens is too long, because the lens is too flat and its converging power is too low; (2) the eyeball is too short, so the retina is nearer the lens than it should be. Corrective lens: a convex (converging) lens of suitable power.

    Step-by-step solution →
13. Q173 CBSE 2023
    A ​narrow beam XY ​of white light is passing through a glass ​prism ABC as shown ​in the ​diagram : Trace it on your answer sheet and show the ​path ​of the emergent beam as observed ​on the screen PQ. Name the phenomenon observed and state its cause.

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    White light splits into seven colours on the screen: dispersion, caused by a different refractive index of glass for each colour.

    The beam bends towards the base $BC$ at $AB$, bends towards the base again at $AC$, and leaves the prism as a band of seven colours that falls on the screen $PQ$: red, orange, yellow, green, blue, indigo and violet, with red the least deviated (nearest the apex side of the band) and violet the most deviated (nearest the base side). The phenomenon is **dispersion** of light. Cause: white light is a mixture of seven colours and the refractive index of the glass is different for each of them - largest for violet and smallest for red. Each colour therefore travels at its own speed in glass, is refracted through its own angle and is deviated by its own amount, so the colours come out along different directions and separate.

    Step-by-step solution →
14. Q174 CBSE 2023
    Observe the ​following diagram and answer the ​questions following ​it :

    1. (i)Identify the defect of vision shown.
    2. (ii)​List its ​two causes.
    3. (iii)Name ​the ​type of ​lens used for the correction of this defect.

    Show answer

    Myopia; caused by an over-curved eye lens or an elongated eyeball; corrected by a concave lens.

    (i) The defect is myopia, also called short-sightedness or near-sightedness: light from a distant object is brought to a focus in front of the retina. (ii) Its two causes are excessive curvature of the eye lens, which makes its converging power too great, and elongation of the eyeball, which puts the retina too far behind the lens. (iii) It is corrected with a concave (diverging) lens of suitable power.

    Step-by-step solution →
15. Q175 CBSE 2023
    1. (i)What is ​the (I) least distance of distinct vision, and (II) far ​point of a normal human eye?
    2. (ii)A student ​is unable to see distinctly a chart hanging on the ​wall of his classroom. Name ​the defect of ​vision he ​is suffering from and the type of corrective lens he ​must use in his spectacles.
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    Near point 25 cm and far point at infinity; the student has myopia and needs a concave lens.

    (i) (I) The least distance of distinct vision of a normal human eye is about $25$ cm. (II) Its far point is at infinity. (ii) The student is suffering from myopia (short-sightedness or near-sightedness), in which the image of a distant object is formed in front of the retina. He must use a concave (diverging) lens of suitable power in his spectacles.

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16. Q176 CBSE 2023
    A student ​cannot see ​distinctly ​the ​charts hanging in ​the science laboratory. Name the defect ​of vision he/she is suffering from. List two causes of this defect. Suggest the type of lenses for ​the modification ​of this defect.
    Show answer

    Myopia, caused by an over-curved eye lens or an elongated eyeball, is corrected by a concave lens.

    Defect: myopia (short-sightedness or near-sightedness). The image of a distant object is formed in front of the retina. Two causes: (i) excessive curvature of the eye lens, so that its converging power is too great (its focal length is too short); (ii) elongation of the eyeball, so that the retina lies behind the position of the image. Correction: a concave (diverging) lens of suitable power.

    Step-by-step solution →
17. Q177 CBSE 2023
    It is ​observed that the power of an eye to see nearby objects as well as far off objects diminishes ​with age.

    1. (i)Give ​reason for the above statement.
    2. (ii)Name the defect that is likely to arise in the eyes ​in such a ​condition.
    3. (iii)Draw a ​labelled ​ray diagram to show the type of corrective lens used for restoring ​the vision of such an eye.
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    With age the ciliary muscles weaken and the lens loses flexibility; presbyopia, corrected by a bi-focal lens.

    (i) With age the ciliary muscles become weak and the eye lens loses its flexibility, so the eye lens can no longer change its curvature freely. The power of accommodation of the eye therefore decreases: the near point recedes and distant vision may also be affected. (ii) The defect is presbyopia (old-age long-sightedness). (iii) The corrective lens is a **bi-focal** lens - a single spectacle lens made of two parts. Its upper portion is a concave (diverging) lens, which is used for distant vision, and its lower portion is a convex (converging) lens, which is used for near vision.

    Step-by-step solution →
18. Q178 CBSE 2023
    The ​colour of clear ​sky ​from the earth appears ​blue but ​from the space it ​appears ​black. ​Why ?
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    Air scatters blue light towards us, so the sky looks blue; space has no atmosphere to scatter light, so it looks black.

    The colour we see when we look at the sky is sunlight that has been scattered towards our eyes. The molecules of air and other fine particles in the atmosphere are much smaller than the wavelength of visible light, and such particles scatter short wavelengths far more strongly than long ones, the scattered amount going roughly as $1/{\lambda }^4$. Seen from the earth, the blue part of sunlight is therefore scattered all over the sky and reaches the eye from every direction, so the clear sky appears blue. In space there is no atmosphere, so there are no molecules or particles to scatter the sunlight. No scattered light reaches the observer's eye from any direction, and the sky therefore appears black.

    Step-by-step solution →
19. Q179 CBSE 2023
    Write the main ​function ​of each of the ​following in the ​human eye :

    1. (i)Cornea
    2. (ii)​Iris
    3. (iii)​Retina
    4. (iv)Ciliary ​muscles
    Show answer

    Cornea refracts light, iris controls pupil size, retina forms the image and sends signals, ciliary muscles adjust the lens focal length.

    (i) Cornea: the transparent front part of the eye, at whose outer surface most of the refraction of the light entering the eye takes place. (ii) Iris: the coloured muscular diaphragm that controls the size of the pupil, and so regulates the amount of light entering the eye. (iii) Retina: the light-sensitive screen at the back of the eye on which a real, inverted image is formed, and whose cells send the signals to the brain through the optic nerve. (iv) Ciliary muscles: they change the curvature and hence the focal length of the eye lens, so that objects at different distances can be focused on the retina (accommodation).

    Step-by-step solution →
20. Q180 CBSE 2023
    A person ​cannot see distinctly the objects placed at the least distance of distinct vision ​for a normal eye. However, ​he can easily read a newspaper by placing it at ​a ​distance ​of 40 cm from his eyes. Name the defect of vision in this case. ​List its two causes. Suggest the type of lenses for his spectacles.
    Show answer

    Hypermetropia (near point at 40 cm), caused by a long focal length or a small eyeball; corrected by a convex lens.

    Defect: hypermetropia (long-sightedness or far-sightedness). The near point has receded from $25$ cm to $40$ cm, and the image of a near object is formed behind the retina. Two causes: (i) the focal length of the eye lens is too long, that is, the converging power of the eye lens has decreased; (ii) the eyeball has become too small (too short from front to back). Correction: a convex (converging) lens for his spectacles. For a normal reading distance of $25$ cm it works out at $f=+66.7$ cm, that is a power of $+1.5$ D.

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