NCERT Class 10 Science Chapter 11 The Human Eye and the Colourful World Extra Questions and Answers
Class 10 Science Chapter 11 Extra Questions and Answers – The Human Eye and the Colourful World. Here in this Page Class X Students can Learn Extra Questions & Answer 11th Chapter Science fully Inside.
We Provided Here The Human Eye and the Colourful World Science Chapter 11 Long Answer Type Question, Very Short Type Questions (VSA) / Multiple Choice Type Questions, Short Type Questions (SA).
Class 10Science Chapter 11 Extra Question with Answer – The Human Eye and the Colourful World
Science Chapter 11 The Human Eye and the Colourful World Class 10 Inside 5 Marks, 3 marks, 2 Marks & And 1 Marks Important Questions and Answers.
1) Fill in the blanks.
1.) Light enters the eye through a thin membrane called as _____.
Ans:
Light enters the eye through a thin membrane called as cornea.
2.) The size of the pupil is controlled by the dark muscular diaphragm called as_____.
Ans:
The size of the pupil is controlled by the dark muscular diaphragm called as iris.
3.) ______ has enormous number of light sensitive cells.
Ans:
Retina has enormous number of light sensitive cells.
4.) The ability of the eye lens to adjust the focal length is called as____.
Ans:
The ability of eye lens to adjust the focal length is called as accommodation.
5.) Myopia is also called as______.
Ans:
Myopia is also called as near- sightedness.
6.) Hypermetropia is also called as ______.
Ans:
Hypermetropia is also called as far-sightedness.
7.) The twinkling of stars is due to the atmospheric _________ of light.
Ans:
The twinkling of stars is due to the atmospheric refraction of light.
2) Multiple choice questions:
1.) The amount of light entering the human eye is controlled and regulated by
a) iris
b) retina
c) pupil
d) cornea
Ans:c) pupil
Explanation: Because, the amount of light entering the human eye is regulated and controlled by the pupil.
2.) The normal eye can see objects clearly which are between
a) 25 cm
b) 25m
c) infinity
d) 25cm and infinity
Ans:
d) 25cm and infinity
3.) In myopic eye the image of the object is formed
a) on the retina
b) behind the retina
c) in front of retina
d) none
Ans:
c) in front of the retina
3.) Concave lens of proper focal length is used for correcting
a) myopia
b) hypermetropia
c) presbyopia
d) a and b
Ans:
a) myopia
4.) In hypermetropia the image of the object is formed
a) in front of the retina
b) on the retina
c) behind the retina
d) a and b
Ans: c) behind the retina
5.) Convex lens of proper focal length are used for correcting
a) myopia
b) hypermetropia
c) presbyopia
d) none
Ans:b) hypermetropia
6.) The defect which is caused due to the gradual weakening of the ciliary muscles and diminishing flexibility of the eye lens is called as
a) myopia
b) hypermetropia
c) presbyopia
d) cataract
Ans:c) presbyopia
7.) To correct presbyopia the lenses are used
a) concave lens
b) convex lens
c) Plano cancave lens
d) bi- focal lens
Ans: d) bi focal lens
8.) A rainbow is always formed in a direction
a) in the direction of sun
b) in a opposite direction of the sun
c) both a and b
d) none
Ans: b) in the opposite direction of the sun
9.) The blue colour of the sky is due to
a) refraction of light
b) dispersion of light
c) scattering of light
d) reflection of light
Ans: c) scattering of light
10.) Which colour is more scattered by particles in air
a) red having longer wavelength
b) blue having shorter wavelength
c) violet
d) green
Ans:b) blue having shorter wavelength
3) Very short answer questions:
1.) What is the function of iris in human eye?
Ans:
Iris is located behind the cornea which is a dark muscular diaphragm which controls the size of the pupil mainly.
2.) What happens when ciliary muscles get relaxed and get contracted?
Ans:
- When ciliary muscles get relaxed then the lens becomes thin due to which focal length get increased and we can easily see distant objects clearly.
- When we see the objects which are near to our eye then ciliary muscles get contracted due to which curvature of the eye lens get increased and eye lens becomes thicker and hence focal length decreases which enables us to see objects which are placed near to our eyes.
3.) What is cataract and how it is corrected?
Ans:
- At old age, the crystalline lens of people becomes milky and cloudy which is called as cataract and it causes the partial or complete loss of vision.
- And to get recovered from this defect the Dr suggests a cataract surgery.
4.) What is myopia?
Ans:
Myopia is the near sightedness and the person suffering with myopia may see objects placed near but cannot see the objects which are at a distant apart.
5.) What is hypermetropia?
Ans:
Hypermetropia is the far sightedness and person suffering with hypermetropia may see the objects which are at a distant apart and cannot see the objects distinctly which are near or closer to our eyes.
6.) What are the causes of myopia?
Ans:
Myopia is arising due to the following issues:
- excessive curvature of the eye lens
- elongation of the eye balls
In case you are missed :- Previous Chapter Extra Questions
7.) What are the causes of hypermetropia?
Ans:
The hypermetropia may causes due to following reasons:
- the focal length of the eye lens is too long
Or
- the eyeballs get becomes too small.
8.) What is presbyopia?
Ans:
- As the age is increasing the power of accommodation of eye get deceased. Due to which the near point gradually receded away and is called as presbyopia.
The people suffering from presbyopia has difficulty in seeing nearby objects comfortably and distinctly without using corrective eye glasses.
4) Short answer questions:
1.) Identify the defect shown by following diagram and draw a diagram of correcting that defect.
a)
(b)
Ans:
As in figure a) the image of the object is formed in front of the camera that means the diagram shows the myopic eye. To correct this defect a concave lens of proper focal length is used.
The following diagram shows the correction of myopia using a concave lens.
Fig. correction in myopia using concave lens
b) The figure b) shows the image of the object which is formed behind the retina. That means the diagram shows the hypermetropic eye. To correct this defect a convex lens of proper focal length is used.
the following diagram shows the correction in hypermetropic eye using convex lens of proper focal length.
Fig. correction for hypermetropia using convex lens
2.) Explain twinkling of stars in detail.
Ans:
- The position of the star as seen by us is its apparent position which changes continuously, due to which we see twinkling of stars.
- This is due to the refraction of starlight through earth’s atmosphere. The light coming from star undergoes numbers of refraction continuously through earth’s atmosphere due the variation of refractive index in layers of atmosphere.
- Due to which the starlight get bends towards normal & the position of star is different from its actual position.
- When viewed from the horizon the position of star appears slightly higher than the actual position.
- This apparent position of the star does not remains constant it changes continuously due to changes in the condition of atmosphere.
- The star is at large distant apart from our eye which acts as a point source of light. The light coming from star reaching to our eyes gets flicker due to which it appears brighter sometime and fainter sometime.
- And this is called as twinkling of stars.
- The following fig. explains the twinkling of stars in detail.
Fig. twinkling of stars
3.) Draw a neat labelled diagram showing refraction of light through glass prism.
Ans:
The following figure shows the neat labelled diagram of refraction of light through triangular glass prism.
Fig. Refraction of light through triangular glass prism
4.) Draw a neat and labelled diagram of human eye and write the functions of cornea, iris and pupil.
Ans:
Cornea:
- Light is entering the eye through a thin membrane which we called cornea.
- And most of the light get refracted at the outer surface of cornea.
Iris:
- Iris is located behind the cornea which is a dark muscular diaphragm and controls the size of the pupil.
Pupil:
- Pupil controls and regulate the amount of light entering the eye.
The following figure shows the neat labelled diagram of human eye.
Fig. neat labelled diagram of human eye
5.) If the person suffering from vision defect uses a lens of power -4D then which type of defect he has?
Ans:
- Given that, the person suffering from vision defect uses a lens of -4D which is a negative.
- We know that, power of lens is the reciprocal of the focal length of the lens.
- Hence, P= 1/f
- Hence, focal length is also negative which says that the person uses concave lens.
- And we know that, concave lens is used in correcting the defect called as myopia.
- Thus, the person is suffering from myopia.
6.) Explain the formation of rainbow with labelled diagram.
Ans:
- After rainfall the sky is fully clear and clouds are in the opposite direction to that of sun, so that sunlight is bright.
- After raining the atmosphere is filled with small water droplets, and this each drop of water acts as a tiny prism.
- When the sunlight is passed through this raindrop at right angle then it splits into spectrum of seven colours which we called as rainbow.
- The rainbow is always formed at opposite side of the sun.
Fig. formation of rainbow
7.) What is the condition to get a white light which is incident on one prism will be comes out as white light through second prism?
Ans:
- Isaac Newton was the first person who used glass prism to obtain spectrum of light.
- He passed the white light through glass prism and obtained spectrum of light containing seven colours.
- Again, he passed this spectrum of light through second identical prism to split these seven colours again, but he was observed that when two identical prisms are placed inverted to each other as shown in fig. above then after emerging light beam from second prism does not contains spectrum of light and it becomes wholly the white light.
- From this experiment he concludes that sunlight is made up from seven colours which are VIBGYOR.
5) Long answer questions:
1.) Explain atmospheric refraction with twinkling of stars.
Ans:
- The position of the star as seen by us is its apparent position which changes continuously, due to which we see twinkling of stars.
- This is due to the refraction of starlight through earth’s atmosphere. The light coming from star undergoes numbers of refraction continuously through earth’s atmosphere due the variation of refractive index in layers of atmosphere.
- Due to which the starlight get bends towards normal & the position of star is different from its actual position.
- When viewed from the horizon the position of star appears slightly higher than the actual position.
- This apparent position of the star does not remain constant it changes continuously due to changes in the condition of atmosphere.
- The star is at large distant apart from our eye which acts as a point source of light. The light coming from star reaching to our eyes gets flicker due to which it appears brighter sometime and fainter sometime.
- And this is called as twinkling of stars.
2.) A person having vision defect uses a lens of power +4D for correcting defect. Then which defect he has and what is nature of lens. Find focal length of the lens.
Ans:
- Given that, the person is having vision defect and to correct it he uses a lens of power +4D. That means he is using a convex lens as convex lens has positive power.
- And we know that, convex lens will be used to correct the defect hypermetropia.
- Hence, the person is suffering from hypermetropia and the nature of the lens he using is the convex lens.
- We know that, the power of the lens is the reciprocal of the focal length of the lens.
Thus, P= 1/f
Hence, f= 1/P = 1/4 = 0.25 m = 25cm
- Thus, the person suffering from hypermetropia and for correcting it he uses a convex lens of focal length 25cm.
3.) Why the dangerous points are indicated by red colour mostly?
Ans:
- As we know that, the wavelength and velocity of the red light is highest. Due to which it travels faster and also the scattering of red colour is less by the smoke or fog and hence we can see it easily from larger distance also.
- In this way, the accidents or danger zone will be indicated to people directly and easily.
- Because of the above all reasons red colour is preferred for indicating danger zone.
4.) A child while playing with his father thrown the spec of his father. Now father is not able to read the newspaper. Then identify the defect of vision and how it was corrected. Draw a ray diagram of the defect and also correcting diagram of the defect.
Ans:
- As the father of child is not able to read newspaper means he can’t see the nearby objects clearly. That means the father of child is suffering from the defect hypermetropia.
- In this defect, the near point becomes farther away from the normal near point.
- And his spec was made up from convex lens of proper focal length to correct his defect.
- The following diagram shows the hypermetropic eye.
Fig. hypermetropic eye
- The following is diagram which shows corrected hypermetropic eye.
Fig. Correction for hypermetropic eye using convex lens
5.) Explain any three-phenomenon related to scattering of light happening in daily life.
Ans:
Following are the phenomenon which happens in environment due to scattering of light.
1.) Blue colour of the sky:
- The blue colour of the sky is due to scattering of light by molecules of air and dust particles whose size is very small as compared to wavelength of light.
- The wavelength of blue & violet light is small & their scattering is more when the light is passed through them than other colours.
- According to Rayleigh’s scattering,
Scattering of light α 1/ λ4
- Hence, less the wavelength of light more is the scattering.
- The order is, λv<λb….<λr and hence the violet & blue colours are scattered more in atmosphere but violet light is not more sensitive to our eyes and we see blue colour mostly, so the sky appears blue.
2.) Deep blue colour of ocean:
- According to Rayleigh’s scattering,
Scattering of light α 1/ λ4
- Hence, less the wavelength of light more is the scattering.
- The order is, λv<λy<λr and hence other colors get absorbed by the water and only more scattered light by water is blue. Hence the water of deep sea appears blue due to scattering of light.
3.) Appearance of the sun reddish at sunrise and sunset and also white at noon:
- The sun appears reddish at the time of sunset or sunrise while appears white at noon.
- At the time of sunset or sunrise, the sun is very near to horizon. So it needs to travel longer distance through atmosphere to reach the observer on earth.
- During this, the blue and violet light are scattered more and away from the path of light & hence, cannot reach the observer directly. The light reaching to observer is only red light. And hence sun appears reddish at the time of sunset or sunrise.
- At noon the sun is at overhead, so the light coming from the sun travels shorter distance in atmosphere.
- And at that time only a small amount of blue and violet coloured light are scattered, due to which sun appears white at noon.
- The diagram below explains the above discussed topic.
In case you are missed :- Next Chapter Extra Questions