Please see Chapter 11 Human Eyes and Colourful World Exam Questions Class 10 Science below. These important questions with solutions have been prepared based on the latest examination guidelines and syllabus issued by CBSE, NCERT, and KVS. We have provided Class 10 Science Questions and answers for all chapters in your NCERT Book for Class 10 Science. These solved problems for Human Eyes and Colourful World in Class 10 Science will help you to score more marks in upcoming examinations.
Exam Questions Chapter 11 Human Eyes and Colourful World Class 10 Science
ONE MARK QUESTIONS
Question: Which liquid fills the space behind the cornea?
Answer: Aqueous humour is filled in the space behind the cornea.
Question: Name the essential parts of human eye,
Answer: (a) Retina (6) Eye lens (c) Cornea (d) Pupil (e) Iris
Question: What is eye lens made of ?
Answer: Eye lens is made of transparent and flexible jelly like material.
Question: Which part of the eye controls the amount of light entering the eye?
Answer: Pupil controls the amount of light entering the eye.
Question: Which liquid fills the space between eye lens and retina?
Answer: Vitreous humour.
Question: Why is blind spot so called?
Answer: An image formed at this point is not sent to brain.
Question: How is the sense of vision carried from the eye to the brain?
Answer: Through optical nerve, sense of vision is carried fromeye to the brain.
Question: What is meant by far point?
Answer: The farthest point upto which an normal human eye can see objects clearly is known as far point.
Question: What is the number of receptors contained in the retina?
Answer: Retina contains more than 125 millions receptors which are of two types, rods and cones.
Question: When you enter from a bright sunshine into a dark room, you are not able to see clearly for sometime, why?
Answer: In bright light, pupil had become small.
Question: Why can you not see an object clearly if it is placed very close to your eye?
Answer: For a human eye, there is a near point, 25 cm. If the distance of the object is lesser than this distance, eye cannot see object clearly.
TWO MARKS QUESTIONS
Question. Why do we observe difference in colours of the sun during sunrise, sunset and noon?
Answer :
During the sunrise or sunset, the sun is at horizon. Most of the blue light and other light of shorter wavelength are scattered most. Only the longer wavelength (red) reaches to us. That’s why sun appears red during the sunrise or sunset.
At noon, the Sun appears white because it is at our head and all wavelength reaches to us due to little of the blue and violet colours are scattered due to least distance travelled by fight.
Question. Why do we observe the seven colours when white light passes through a glass prism? Which component of white light deviates the least?
Answer : Since angle of deviation for different colour is different hence different colour suffers different deviation.
Deviation for red colour is minimum.
Question. Sushil went to an eye specialist for check up. He prescribed him to use spectacle lens of + 0.5D power.
a. Name the defect of vision he is suffering from.
b. Find the focal length of spectacle lens.
Answer :
a. Hypermetropia.
b. Power of spectacle P = + 0.5D
f = 1/P = +1/0.5 . m or f =+ 2 m positive sign means it is a convex lens.
Question. State the function of pupil and ciliary muscles.
Answer :
a. Pupil controls the amount of light entering the eye.
b. Ciliary muscles help in accommodation of power of eye lens.
Question. Draw a neat diagram to show the refraction of a light ray through a glass prism, and label on it the angle of incidence and angle of deviation.
Answer :
EF–Refracted ray +r –Angle of refraction
FS–Emergent ray +e–Angle of emergence
+A–Angle of prism +D–Angle of deviation
Question. (a) What is ‘power of accommodation of the eye?
(b) What happens to the image distance when the object being viewed is moved away from the eye?
Answer :
(a) Power of accommodation of the eye means the ability to change the focal length of the eye lens to see near and distant objects.
(b) Image distance remains fixed which is equal to distance between retina and eye lens.
Question. (a) What is meant by least distance of distinct vision?
(b) How does the thickness of the eye lens change when we shift looking from a distant tree to reading a book?
Answer :
(a) Least distance of distinct vision means the minimum distance upto which an eye can see clearly.
(b) To see distant object focal length of eye lens must be more so it becomes thinner when we want to read a book eye lens is comparatively thicker.
Question. What is dispersion of light? Name the (i) component of white light that deviates the least, (ii) component of white light that deviates the most, while passing through a glass prism.
Answer : a. Splitting of white light into its constituent colours when passed through a prism called dispersion of light.
b. Violet colour deviates the most while passing through the glass prism.
Question. Why does it take sometimes to see the objects in a dim room when we enter the room from bright sunlight outside?
Answer : In bright sunlight, pupil of eye contracts to control the light. When we enter a dim room, pupil takes some time to expand to allow more light to see the objects clearly.
Question. A 14 year old student is not able to see clearly the questions written on the blackboard placed at a distance of 5 m from him.
a. Name the defect of vision he is suffering from.
b. With the help of labelled ray diagrams show how this defect can be corrected.
c. Name the type of lens used to correct this defect.
Answer :
a. Myopia
b.
Question: How can change of size of eyeball be one of the reason for: (a) Myopic (b) Hypermetropic Compare the size of eyeball with that of a normal eye in each case. How does this change of size affect the position of image in each case?
Answer: (a) The eye suffering from myopia, has long eye ball than that of normal eye due to which the retina is at a larger distance from the eye lens. This results in the formation of the image in front of the retina.
(b) The eye suffering from hypermetropia has short eye ball than that of normal eye due to which the retina is smaller distance from the eye lens. This results in the formation of the image behind the retina.
Question: State the function of pupil and ciliary muscles.
Answer: a. Pupil controls the amount of light entering the eye.
b. Ciliary muscles help in accommodation of power of eye lens.
Question: Sushil went to an eye specialist for check up. He prescribed him to use spectacle lens of + 0.5D power. a. Name the defect of vision he is suffering from.
b. Find the focal length of spectacle lens.
Answer: a. Hypermetropia.
b. Power of spectacle P = + 0.5D
f =1/p = +1/0.5 m
or f =+2 m positive sign means it is a convex lens.
Question: What is meant by persistence of vision?
Answer: On removing object seen, its impression persists on the retina for 16 1 th second. The inability of human brain to perceive more than two images formed on the retina within interval of 1/16 th of a second is called persistence of vision. In this case, both the images merge and give a sensation of continuity.
Question: A child sitting in a classroom is not able to read clearly the writing on the blackboard.
a. Name the type of defect from which his eye is suffering.
b. With the help of a ray diagram show how this defect can be remedied.
Answer: a. Myopia
b. Myopia can be remedied by using concave lens.
Question: Mention the factor on which scattering of light depends. Why does the sky appear dark in space?
Answer: Scattering of light depends on the presence of atmosphere which contains water droplets, molecules of air, smoke and dust particles. In the space, there is no atmosphere to scatter light.
Question: What is meant by least distance of distinct vision? How does this vary between the very young and old people?
Answer: Least distance of distinct vision is the minimum distance between eye and object to see it clearly.
In young, the least distance of distinct vision is lesser and for old people it is more.
Question: List four common defects of vision that can be corrected with the use of spectacles.
Answer: (i) Myopia (ii) Hypermetropia (iii) presbyopia (iv) Astigmatism.
Question: Define dispersion of white light and name the colours of white light in order.
Answer: When white light is passed through a prism, it splits into its seven constituent colours. Splitting of white light into its constituent colours is called dispersion.Seven constituent colours are – violet, indigo, blue, green, yellow, orange and red. (VIBGYOR).
Question: Describe an experiment to discuss the recombination of dispersed light.
Answer: If another identical prism is placed in inverted position in front of a prism then dispersed colours obtained from first prism get recombine to produce white light.
Question: Explain why do stars twinkle and planets do not?
Answer: The light coming from star get refracted through the atmospheric layers. Due to this, the star appear slightly higher than its actual position. Since the densities of atmospheric layers changes frequently and hence the position of the star appear changes continuously stars are very distant point-sized objects. As the path of rays of light coming from star is continuously changes.
So sometimes light enters into our eyes and some times it faints. This is twinkling of the star. Since planets are closer to us, their size is also big. Our eyes receive light from different points of the planets. Hence planets do not twinkle.
Question: (a) Explain how a normal human eye is able to see distinctly the object placed at a distance as well as those placed at a nearer distance.
(b) What is the far point and near point of a normal human eye?
Answer: (a) Ciliary muscles change the curvature of eye lens as per requirement of the eye. This changes the focal length of eye lens. When muscles are relaxed, lens becomes thin and distant objects are seen clearly.
While seeing closer objects, muscles contract, this thickens the eye lens and focal length decreases.
(b) Far point — Infinity. Near point — 25 cm from the eye.
Question: Draw a neat diagram to show the refraction of a light ray through a glass prism, and label on it the angle of incidence and angle of deviation.
Answer: EF–Refracted ray ∠r –Angle of refraction
FS–Emergent ray ∠e–Angle of emergence
∠A–Angle of prism ∠D–Angle of deviation
Question: A 14 year old student is not able to see clearly the questions written on the blackboard placed at a distance of 5 m from him.
a. Name the defect of vision he is suffering from.
b. With the help of labelled ray diagrams show how this defect can be corrected.
c. Name the type of lens used to correct this defect.
Answer:
a. Myopia
b.
c. Concave lens
FIVE MARKS QUESTIONS
Question. (a) Calculate maximum power of accommodation of a person having normal vision.
(b) A person needs to use glasses for reading newspaper. Identify the defect in her vision and the type of lens she would need to correct it.
(c) Sometimes when we enter into a dark room from bright sunlight we are unable to see objects clearly. Why?
Answer :
(a) Least distance of distinct vision for a normal eye
D = 25 cm.
p = 1/f = 100/25 = 4D
For a person having normal vision, the power of accommodation is 4 D.
(b) Hypermetropia, to correct hypermetropia convex lens is needed.
(c) In bright light the pupil contract its size becomes small to control the light, but when we enter into a dark room it take sometime for the pupil to expand to allow more light in dark room.
Question. State one function each of iris, pupil, and cornea.
Answer :
a. Iris: It controls the amount of light entering the eye by changing the size of pupil.
b. Pupil: Pupil is a part of the eye through which light enters in the eye.
c. Cornea: It is a thin membrane which covers the eye ball. Light enters the eye through cornea where it is refracted most.
Question. (a) Write the function of each of the following parts of human eye:
(i) Cornea (ii) Iris
(iii) Crystalline lens (iv) Ciliary muscles
(b) Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an astronaut on the Moon? Give reason to justify your answer.
Answer :
(a) Function of Human eye:
(i) Cornea focuses light ray to enter the eye.
(ii) Iris control and regulate amount of light nentering the eye and control the size of pupil.
(iii) Crystalline lens is like a convex lens which converge light rays on the retina.
(iv) Ciliary muscles adjust focal length of eye lens by contraction and relaxation so that sharp image can be obtained on the retina.
(b) During morning and evening time, sun is at the horizon, sunlight has to travel longer distance in atmosphere. Violet and blue colours etc. of shorter wavelength scatter in the space only. The longer wavelength red colour reaches to the observer on earth and sun appears reddish.
No, because there is no atmosphere on moon and no scattering of light takes place there.
Question. (a) With the help of a suitable diagram explain whythe Sun is visible to us two minutes before the actual sunrise and two minutes after the actual sunset.
(b) Name the phenomenon responsible for apparent flattening of the Sun’s disc at sunrise and sunset.
Answer :
(a) The duration of the day becomes approximately 4 minutes longer due to atmospheric refraction. We can see the sun when it is below the horizon in the morning. The rays of light from the sun below the horizon(s) reach to our eyes due to refraction of light 2 minutes before it actually rises. Similarly the sun can be seen about 2 minutes after it actually set. Thus the duration of day time increases by 4 minutes (2 minutes each time at the time sunrise or sunset).
Question. Study the diagram and answer the questions the follows :
Answer :
a. Identify the defect of vision represented by this diagram.
b. List the two possible causes of this defect.
c. With the help of ray diagram explain how this defect can be corrected.
Answer :
a. The defect of vision is hypermetropia.
b. (i) increase in focal length of eye lens
(ii) shortening of eye ball.
c. Hypermetropia can be corrected by using convex lens.
Question: (a) Write the function of each of the following parts of human eye:
(i) Cornea (ii) Iris
(iii) Crystalline lens (iv) Ciliary muscles
(b) Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an astronaut on the Moon? Give reason to justify your answer.
Answer: (a) Function of Human eye:
(i) Cornea focuses light ray to enter the eye.
(ii) Iris control and regulate amount of light entering the eye and control the size of pupil.
(iii) Crystalline lens is like a convex lens which converge light rays on the retina.
(iv) Ciliary muscles adjust focal length of eye lens by contraction and relaxation so that sharp image can be obtained on the retina.
(b) During morning and evening time, sun is at the horizon, sunlight has to travel longer distance in atmosphere. Violet and blue colours etc. of shorter wavelength scatter in the space only. The longer wavelength red colour reaches to the observer on earth and sun appears reddish.
No, because there is no atmosphere on moon and no scattering of light takes place there.
Question: (a) A student is unable to see clearly the worlds written on the blackboard placed at a distance of
approximately 3 m from him. Name the defect of vision the boy is suffering from State the possible causes of this defect and explain the method of correcting it.
(b) Why do stars twinkle? Explain.
Answer: (a) Defects of vision: Myopia or short sightedness.
Reasons: Excessive curvature of eye lens and elongation of eye ball.
(b) Due to atmospheric refraction stars twinkle. The density of atmospheric layers keep changing due to which point sized star sometimes appear brighter or dimmer with changing position. Due to this, stars appears twinkling.
Question: (a) With the help of a suitable diagram explain why the Sun is visible to us two minutes before the actual sunrise and two minutes after the actual sunset.
(b) Name the phenomenon responsible for apparent flattening of the Sun’s disc at sunrise and sunset.
Answer: (a) The duration of the day becomes approximately 4 minutes longer due to atmospheric refraction. We can see the sun when it is below the horizon in the morning. The rays of light from the sun below the horizon(s) reach to our eyes due to refraction of light 2 minutes before it actually rises. Similarly the sun can be seen about 2 minutes after it actually set. Thus the duration of day time increases by 4 minutes (2 minutes each time at the time sunrise or sunset).
Question: A person can see distant signboards clearly but cannot read clearly a book which is at 25 cm from his eye. Giving reason identify the defect. Draw a labelled ray diagram to illustrate this defect and its correction.
Answer: Eyes defect is hypermetropia. Its causes are due to
a. shortening the eye ball
b. increase in focal length of eye lens.
Question: With the help of scattering of light, explain the reason for the difference in colours of the Sun as it appears during sunrise/sunset and noon.
Answer: At the time of sunrise or sunset it appears red where as at noon it appear white when it is overhead because at sunrise or sunset blue colour and other shorter wavelength light get scattered away while passing through the atmosphere. Scattering of longer wavelength is least which reach to the earth. Due to this sun appears red during morning and evening time.
When sun is overhead at noon, sun rays travels smaller distance, due to little scattering of blue and violet colour wavelength almost all wavelengths reach to earth and due to this sun appears white.
Question: State one function each of iris, pupil, and cornea.
Answer: a. Iris: It controls the amount of light entering the
eye by changing the size of pupil.
b. Pupil: Pupil is a part of the eye through which light enters in the eye.
c. Cornea: It is a thin membrane which covers the eye ball. Light enters the eye through cornea where it is refracted most.
Question: What is meant by scattering of light? Use this phenomenon to explain why the clear sky appears blue or the sun appears reddish at sunrise.
Answer: a. Scattering of light is phenomenon by which beam
of light is spreaded in many direction when itinteracts with particle of matter. When sunlight strikes molecules in atmosphere, the light is redirected in many direction.
b. Scattering of blue colour is most due to shorter wavelength, where as scattering of red colour is least. All colours scattered in the sky and red colour light reaches to earth, due to this sun appears reddish.
Question: State the cause of dispersion, when white light enters a glass prism. Explain with a diagram.
Answer: When white light passes through a prism it splits into its constituent colours, because each coloured light has different speed in prism. Prism has different refractive index for these light rays and so deviates through different angles when emerge out from the prism.
Deviation for violet colour (shortest wavelength) is most and for red colour (largest wavelength) deviation is least.
Question: (a) Calculate maximum power of accommodation of a person having normal vision.
(b) A person needs to use glasses for reading newspaper. Identify the defect in her vision and the type of lens she would need to correct it.
(c) Sometimes when we enter into a dark room from bright sunlight we are unable to see objects clearly. Why?
Answer: (a) Least distance of distinct vision for a normal eye
D = 25 cm.
p=1/f=100/25=4D
For a person having normal vision, the power of accommodation is 4 D.
(b) Hypermetropia, to correct hypermetropia convex lens is needed.
(c) In bright light the pupil contract its size becomes small to control the light, but when we enter into a dark room it take sometime for the pupil to expand to allow more light in dark room.
Question: A person cannot see objects farther than 12 m from the eye clearly. Name the defect of vision he is suffering from and the lens that should be used for correction of this defect. Illustrate with the help of a diagram, how this lens will correct the defective vision?
Answer: He is myopic. Myopia can be corrected by using concave lens.
Question: A person cannot read a book at distances less than 50 cm. Name the defect of vision he is suffering from.
How can it be corrected? Draw ray diagrams to show the image formation:
a. by defective eye and
b. after using corrective lens.
Answer: a. Either the hypermetropic eyeball is too short or
b. The ciliary muscle is unable to change the shape of the lens enough to properly focus the image i.e., the focal length of the eye lens is too long. This defect is called hypermetropia.
It can be corrected with the help of a convex lens as shown.
Question: A person is unable to read a book clearly when kept at a distance of 25 cm from his eye. Name the defect.
How can it be corrected? Draw ray diagrams for (i)defective eye (ii) corrected eye and explain them.
Answer: The person cannot read a book at a distance of 25 cm from his eyes. So he is suffering from long sightedness/ hypermetropia. It can be corrected by using convex lens of suitable focal length.
Question: (a) Explain the phenomenon of scattering of light.
State the factor on which colour of scattered light depends.
(b) List any two natural phenomenon based on scattering of light.
Answer: (a) Scattering of light is the phenomenon due to which light gets deflected by the atoms or molecules of different atmospheric gases and suspended particles present in atmosphere. Scattering depends upon size of the particles of the medium through which light passes.
(b) Two natural phenomenon based on scattering are (i) Reddish colour of sky during sunrise and sunset, (ii) Blue colour of sky.
Question: With the help of a diagram, explain the formation of a rainbow in the sky.
Answer: The water droplets in the atmosphere act like small prisms. These droplets refract and disperse the incident sunlight, then reflect it internally and finally refract it again when it comes out of the rain drop.
Due to distortion of sunlight and internally reflection, different colours reach to the observer.
Question: (a) A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.
(b) Why do stars twinkle? Explain.
Answer: (a) He is suffering from myopia. Causes of myopia:
(i) elongation of eye ball.
(ii) excessive curvature of cornea.
Concave lens of suitable power is used to correct myopia.
(b) Light coming from stars when enter in the Earth’s atmosphere suffers refraction from the atmospheric layers. Since the densities of atmospheric gases changes frequently. Since the stars are point sized and at a far distance so sometimes star appear brighter and sometimes dimmer which gives the impression as the stars twinkling.
Question: (a) What is meant by dispersion of white light? Draw a diagram to show the dispersion of white light by a glass prism.
(b) Light of two colours A and B pass through a prism. A deviates more than B from its path of incidence. Which colour has a higher speed in the prism?
Answer: (a) Splitting of white light into its constituent colours when it is passed through a prism is called dispersion of white light.
(b) B
Question: (a) If a person wears lens of power – 6D for distant vision and for correcting his near vision he needs a lens of +2D. Determine the focal length of the lenses in both the case.
(b) Give reason for the following natural phenomenon:
(i) Stars twinkle
(ii) Planets do not twinkle
(iii) Stars appear raised in the sky.
Answer:
(b) (i) Due to continuous changes in the densities of the atmospheric layers the apparent position of the star also changes; which make the light coming from the distant point sized star brighter and dimmer. The light coming
from the stars therefore gives a shaking appearances, which gives the impression of twinkling of a star.
(ii) Since the planets are closer to us. Due to this they appear a combination of large point-sizes source of light, and change in the path of light coming from the planets is not significant. So planets do not appear twinkling.
(iii) Due to atmospheric refraction, a star appears to be slightly higher than its actual position in sky.
Question: (a) State the reasons which lead to hypermetropia. With the help of suitable diagram, explain this defect of vision and its correction.
(b) Draw diagram of an experimental arrangement for observing scattering of light in colloidal solution. Name the two chemicals used in this activity.
Answer: a. In hypermetropia a person cannot see near by objects clearly. Its is due to shortening of the eye ball or due to increase in focal length of eye lens.
To correct hypermetropia, a convex lens of suitable focal length is needed.
b.
Question: What is meant by scattering of light? Mention the factor on which it depends. Explain why the colour of the clear sky is blue? An Astronaut in space finds sky to be dark. Explain reason for this observation.
Answer: (a) Scattering of light is the phenomenon due to which light gets deflected by the atoms, molecules or particles of the medium when light falls on them. These are known as scatterer particles.
(b) Factors on which scattering depends are the size of the atoms, molecules of the scatterer.
(c) When sunlight falls on the atoms or molecules of the gases shorter wavelengths J like of blue colour get scattered more due to which sky appears blue.
In space there is no atmosphere, so there is no scattering hence the sky appears dark/black.
