The Human Eye and the Colourful World Important Questions: Vision and light play a key role in understanding our surroundings. In Class 10 Science, Chapter 10 explains the structure and function of the human eye, defects of vision, corrective measures, and the behaviour of light leading to phenomena like dispersion, scattering, and the formation of rainbows.
Understanding these concepts is crucial for answering human eye and colourful world important questions, as it helps explain how the eye functions, how we perceive colours, and why natural phenomena like the blue sky, red sunsets, and rainbows occur.
The Human Eye and the Colourful World Important Questions Answers
Boost your preparation for Class 10 Science Chapter 10 with these high-yield questions and answers. Practice concepts like the structure of the eye, accommodation, defects of vision, refraction, dispersion of light, scattering, and rainbow formation. Solving human eye and the colourful world important questions helps you revise efficiently, understand light and vision concepts clearly, and improve accuracy in exams.
Multiple Choice Question [1 Mark]
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Assertion: Sky appears blue in the day time.
Reason: White light is composed of seven colours.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true and R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is False but R is true.
Ans. (B)
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A person went for a medical check-up and found that the curvature of his eye lens was increasing. Which defect is he likely to suffer from?
(A) Myopia (B) Cataract (C) Presbyopia (D) Hypermetropia
Ans. (A) -
When a person moves from a dark room into bright sunlight, which part of the eye reacts first to adjust the amount of light entering?
(A) Retina (B) Iris (C) Lens (D) Pupil
Ans. (B) -
What is the normal near point distance for a human eye?
(A) 25 cm (B) 50 cm (C) 75 cm (D) 100 cm
Ans. (A) -
Which part of the human eye is responsible for the perception of images?
(A) Cornea (B) Iris (C) Lens (D) Retina
Ans. (D) -
Consider a scenario where a person suddenly finds distant objects blurry, especially while driving at night. Which corrective lens should ideally be prescribed?
(A) Convex lenses (B) Concave lenses (C) Bifocal lenses (D) No lenses needed
Ans. (B) -
What causes the sky to appear blue on a clear day?
(A) Reflection of water in the atmosphere.
(B) Dispersion of sunlight by water droplets.
(C) Scattering of blue light more than other colours by the atmosphere.
(D) Absorption of blue light by the atmosphere.
Ans. (C) -
Why do we see a spectrum of colours when white light passes through a prism?
(A) The prism absorbs all colours except one.
(B) Different colours of light are reflected at different angles.
(C) Different colours of light travel at different speeds in the prism, causing them to bend at different angles.
(D) The prism increases the intensity of light.
Ans. (C) -
A man suffering from myopia cannot see the objects distinctly at a distance greater than 2 m. Which lens is required to correct the defect?
(A) –2D (B) +2D (C) –0.5D (D) +0.5D
Ans. (C) -
What happens to the frequency when light passes from one medium to another?
(A) It increases. (B) It remains the same. (C) It decreases. (D) It may increase or decrease.
Ans. (B) -
The eye is more sensitive to yellow colour but why are danger signals painted red instead of yellow?
(A) The scattering of red light is much less than that of yellow light.
(B) The scattering of red light is more than that of yellow light.
(C) Yellow light, when scattered, is brighter.
(D) Red light, when scattered, is brighter.
Ans. (A) -
What type of image is formed on the retina?
(A) Virtual and inverted (B) Real and inverted (C) Virtual and erect (D) Real and erect
Ans. (B) -
When a beam of white light falls on a glass prism, the colour of light which will deviate least is:
(A) Violet (B) Green (C) Blue (D) Red
Ans. (D) -
The splitting of white light into its component colours is called:
(A) Refraction (B) Reflection (C) Dispersion (D) Tyndall Effect
Ans. (C) -
At a particular minimum value of angle of deviation, the refracted ray becomes:
(A) Parallel to base of prism. (B) Perpendicular to base of prism.
(C) Inclined at 45 degrees w.r.t base of prism. (D) None of these
Ans. (A) -
Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
(A) Dispersion of light (B) Scattering of light (C) Total internal reflection of light (D) Reflection of light from the earth
Ans. (B) -
At noon, the Sun appears white as
(A) Blue colour is scattered the most
(B) Red colour is scattered the most
(C) Light is least scattered
(D) All the colours of the white light are scattered away
Ans. (C) -
Which of the following colours is least scattered by fog, dust or smoke?
(A) Red (B) Violet (C) Blue (D) Green
Ans. (A) -
The term "accommodation" as applied to the eye, refers to its ability to:
(A) Control the light intensity falling on the retina.
(B) Erect the inverted image formed on the retina.
(C) Adjust the focal length of the lens.
(D) Vary the distance between the lens and retina.
Ans. (C) -
A man finds it difficult to read the odometer on the dashboard of the car but is able to clearly read a distant road sign. Which of the following statements is correct about this man?
(A) The near point of his eyes has shifted away.
(B) The near point of his eyes has come closer to him.
(C) The far point of his eyes has shifted away.
(D) The far point of his eyes has come closer to him.
Ans. (A)
Very Short Answer Tpe Question [1 Mark]
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A person needs a lens of power –5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
Sol.
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Why does the sky appear dark instead of blue to an astronaut?
Sol. The sky appears dark instead of blue to an astronaut, as scattering of light does not take place outside the earth's atmosphere. -
Explain why the planets do not twinkle.
Sol. Unlike stars, planets don't twinkle. Stars are so distant that they appear as pinpoints of light in the night sky, even when viewed through a telescope. Since all the light is coming from a single point, its path is highly susceptible to atmospheric interference (i.e., their light is easily diffracted). -
Why do stars twinkle?
Sol. The twinkling of a star is due to atmospheric refraction of starlight. The starlight, on entering the earth's atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index.
(i) The angle between the two refracting surfaces of a prism is called
(A) Angle of prism
(B) Angle of incidence
(C) Angle of deviation
(D) Angle of emergence
Ans. (A)
(ii) The angle between the incident ray and the emergent ray is called
(A) Angle of emergence
(B) Angle of deviation
(C) Angle of incidence
(D) None of these
Ans. (B)
(iii) The angle of deviation depends on
(A) Refractive index of the prism
(B) Angle of incidence
(C) Both (A) and (B)
(D) None of these
Ans. (C)
(iv) The rectangular surfaces of a prism are known as
(A) Reflecting surfaces
(B) Dispersing surfaces
(C) Refracting surfaces
(D) None of these
Ans. (C)
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Read the following and answer any four questions from 26(i) to 26(v).
The spreading of light by the air molecules is called scattering of light. The light having least wavelength scatters more. The sun appears red at sunrise and sunset, and the appearance of blue sky is due to the scattering of light. The colour of the scattered light depends on the size of particles. The smaller molecules in the atmosphere scatter smaller wavelengths of light. The amount of scattering of light depends on the wavelength of light. When light from sun enters the earth's atmosphere, it gets scattered by the dust particles and air molecules present in the atmosphere. The path of sunlight entering in the dark room through a fine hole is seen because of scattering of the sunlight by the dust particles present in its path inside the room.
(i) To an astronaut in a spaceship, the colour of earth appears
(A) Red
(B) Blue
(C) White
(D) Black
Ans. (B)
(ii) At the time of sunrise and sunset, the light from sun has to travel
(A) Longest distance of atmosphere
(B) Shortest distance of atmosphere
(C) Both (A) and (B)
(D) Can't say
Ans. (A)
(iii) The colour of sky appears blue, it is due to the
(A) Refraction of light through the atmosphere
(B) Dispersion of light by air molecules
(C) Scattering of light by air molecules
(D) All of these
Ans. (C)
(iv) At the time of sunrise and sunset,
(A) Blue colour is scattered and red colour reaches our eye
(B) Red colour is scattered and blue colour reaches our eye
(C) Green and blue are scattered and orange reaches our eye
(D) None of these
Ans. (A)
(v) The danger signs are made red in colour, because
(A) The red light can be seen from farthest distance
(B) The scattering of red light is least
(C) Both (A) and (B)
(D) None of these
Ans. (C)
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What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.
Sol. After a rain shower, the sunlight gets dispersed by tiny droplets present in the atmosphere. The water droplets act like small glass prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to dispersion of light and internal reflection, different colours reach the observer's eye, which is called a rainbow.
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Why is the Tyndall effect shown by colloidal particles? State four instances of observing the Tyndall effect.
Sol. The phenomenon of scattering of light by the colloidal particles gives rise to the Tyndall effect. When a beam of light strikes colloidal particles, the path of the beam becomes visible. This is known as the Tyndall effect.
This phenomenon can be observed when:
(i) Sunlight passes through a canopy of dense forest, when tiny water droplets in the mist scatter light.
(ii) Torch light is switched on in a foggy environment, light rays are visible after being scattered by the fog particles in the surrounding air.
(iii) A fine beam of sunlight enters a smoke-filled room through a small hole.
(iv) Shining a flashlight beam into a glass of diluted milk produces the Tyndall effect.
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What is 'dispersion of white light'? State its cause. Draw a ray diagram to show the dispersion of white light by a glass prism.
Sol. Splitting of white light into its seven constituent colours due to refraction is known as dispersion of white light.
Cause of dispersion: When a beam of white light enters a prism, it gets refracted and splits into seven constituent colours. The splitting of the light ray occurs due to the different bending angles for each colour. Thus, each colour ray when passing through the prism, bends at different angles with respect to the incident beam, thus giving rise to a spectrum.
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