Kerala SSLC Notes Class 10 Science Vision and the World of Colours
Kerala SSLC Notes Class 10 Science Part 2 Book for Chapter 5 Vision and the World of Colours by SSLC Teacher Kerala Class 10 Board Exam. This SSLC Notes Class 10 Science will help students to prepare for Kerala Syllabus SSLC history, SSLC Geography focus area, sslc Science .
Kerala Education department directly manages 14000+ schools, 160K+ teachers ,20K+ non teaching staff of the state.[Details in Sametham -the complete School Databank, SchoolWiki – Wiki of each Individual schools].The Department plays an eminent role in the physical and mental development of all pupils studying in schools. There has been tremendous growth in educational facilities at all levels of education in the state during the last 50 years. Here we have given Kerala SSLC Notes Class 10 Science Chapter 5 World in the Twentieth for English Medium Kerala Syllabus.
SSLC Notes Class 10 Science – Vision and the World of Colours
Multiple Choice Questions:
1.) The near point of an eye having healthy vision is
a) 25m
b) 25mm
c) 25cm
d) 20cm
Ans: c) 25cm
2.) Light enters in the eye through thin membrane which is named as
a) retina
b) iris
c) cornea
d) pupil
Ans: c) cornea
3.) The ability of our eye lens to adjust the focal length according to light entered is called as
a) myopia
b) hypermetropia
c) presbyopia
d) power of accomodation
Ans: d) power of accomodation
4.) Hypermetropia is also called as
a) near sightedness
b) far sightedness
c) long sightedness
d) both b and c
Ans: d) both b and c
5.) Which of the following colours are primary colours.
a) Yellow, blue, green
b) red, blue, orange
c) red, green, black
d) red, blue, green
Ans: d) red, blue, green
6.) The twinkling of stars is due to atmospheric
a) reflection
b) refraction
c) scattering
d) dispersion
Ans: b) refraction
7.) In case of myopia, the image of the object forms
a) in front of retina
b) on the retina
c) behind the retina
d) cannot predict
Ans: a) in front of retina
8.) In case of hypermetropia which lens is used to correct it
a) concave
b) biconcave
c) convex
d) both a and c
Ans: c) convex
9.) Which type of lens is used to correct myopia
a) concave
b) convex
c) biconcave
d) biconvex
Ans: a) concave
10.) In case of hypermetropia, the image is formed
a) in front of the retina
b) behind the retina
c) on the retina
d) cannot say
Ans: b) behind the retina
11.) Presbyopia is corrected by using which lens
a) concave
b) convex
c) biconcave
d) bi focal lens
Ans: d) bi focal lens
12.) We observe the blue colour of the sky which is due to
a) refraction of light
b) dispersion of light
c) scattering of light
d) both b and c
Ans: c) scattering of light
13.) Why sky appears blue
a) blue colour scatters more
b) blue colour is having shorter wavelength
c) blue colour is having longer wavelength
d) both a and b
Ans: d) both a and b
14.) Myopia causes due to
a) eyeballs get becomes too small
b) elongation of the eyeballs
c) excessive curvature of the eye lens
d) both b and c
Ans: d) both b and c
15.) If a person needs -4.5D power lens, that means he is suffering from
a) hypermetropia
b) presbyopia
c) myopia
d) cataract
Ans: c) myopia
Very Short Answer Questions:
1.) What is dispersion of light?
Ans:
Dispersion is the phenomenon of splitting of composite light into its constituent seven colours i.e. VIBGYOR
2.) What is interrelation between scattering of light and size of particles?
Ans:
The size of particles increases then the rate of scattering also increases. Also, if the size of the particles greater than wavelength of light then the rate of scattering will be same for all colours.
3.) Myopia is caused because of which reasons?
Ans:
Myopia is caused because of the following reasons:
When eyeballs get more elongated.
Due to excessive curvature of the eye lens.
4.) Hypermetropia is caused because of which reasons?
Ans:
Hypermetropia is caused because of the following reasons:
When the focal length of the eye lens becomes too long.
And when eyeballs get becomes too small.
5.) How we can see the nearby objects clearly?
Ans:
- Our eye lens is made up of ciliary muscles which are responsible for modifying curvature of the eye lens.
- Due to change in curvature of the eye lens, focal length of the eye lens also changes.
- While seeing towards the objects which are very close to our eyes, that time ciliary muscles get contracted and hence curvature of the lens increases. Due to which eye lens get becomes thicker and finally focal length of the eye lens decreases and hence we are able to the nearby objects clearly.
6.) How we can see the distant objects clearly?
Ans:
- Our eye lens is made up of ciliary muscles which are responsible for modifying curvature of the eye lens.
- Due to change in curvature of the eye lens the focal length of the eye lens also changes.
- While seeing towards the objects which are distant apart that time this ciliary muscles get relaxed due to which eye lens becomes thinner and hence it’s focal length increases and hence we are able to distant objects clearly.
7.) In what position we have to place the two prisms so that after incidence of white light we will get again white light?
Ans:
- Isaac Newton did this experiment to obtain white light again through two prisms. Initially he sent white light through first prism and the emitted spectrum of seven colours he sent through the second identical prism keeping in mind to get again seven colours. But, he kept both prism inverted to each other and observed that the light coming from second prism is also a white light.
- That means if we are keeping two prisms inverted to each other, that time the light emitted from second prism is also white again.
8.) Why the deviation is different for different colours in dispersion?
Ans:
In dispersion, due to the different wavelengths of different colours the rate of refraction for each colour is different. And this rate of refraction decreases with increase in wavelength. Hence, red light having longer wavelength gets deviated less while violet light having shorter wavelength get deviated more.
9.) Rainbow is formed due to which phenomenon?
Ans:
Rainbow is formed due to internal reflection, refraction and dispersion of light.
10.) Why dispersion occurs?
Ans:
When a light beam is incident obliquely on the prism it undergoes refraction also undergoes refraction when it comes out from the prism. These angle deviation of different light colours is different because of change in wavelength of different colours. And hence the light rays or colours get deviated at different angles and hence separated which we called as a dispersion of light.
11.) Which colours scatters more and why?
Ans:
The colours like violet, indigo and blue scatters more because they are having smallest wavelength in sunlight.
12.) Which colours scatters less and why?
Ans:
The red colour scatters less because red colour is having longer wavelength as compared to other colours in sunlight.
13.) Why red colour is used for indicating dangerous zones?
Ans:
- As we know that, shorter the wavelength more is the scattering and longer the wavelength scattering is less. Red colour is having longer wavelength and hence scatters less and as a result it covers larger distance and easily reaches to our eyes as compared to others.
- Hence, red colour is used for indicating dangerous zones as that colour reaches to our eyes from longer distance also.
14.) The size of pupil is controlled by which part?
Ans:
The size of pupil is controlled by the dark muscular diaphragm called as iris.
15.) What is the function of pupil?
Ans:
The amount of light entering the human eye is mainly regulated and controlled by the pupil.
Short Answer Questions:
1.) How ciliary muscles responsible for vision.
Ans:
- Ciliary muscles by contracting and relaxing according to the object distance helps in vision.
- When ciliary muscles get relaxed that time lens becomes thin which increases focal length and hence we see the objects which are distant apart from us.
- Again, when we are seeing towards the objects near to our eyes that time these ciliary muscles get contracted which causes increase in curvature of eye lens and hence eye lens becomes thicker. Due to which focal length gets decreases which is responsible for seeing objects near to our eyes.
- In this way ciliary muscles helps in vision.
2.) What is hypermetropia, how it causes and how it is corrected.
Ans:
- Hypermetropia is also called as long sightedness. The person suffering from this defect able to see the objects which are distant apart but not able to see the objects clearly which are near or closer to our eyes.
- Hypermetropia is caused because increase in the focal length of eye lens and as eyeballs get becomes too small.
- To correct hypermetropia convex lens of proper focal length is used.
3.) What is myopia? What are the causes and how it can be corrected?
Ans:
- Myopia is also called as near sightedness.
- The person suffering from myopia able to see the objects near to our eyes but not able to see the objects which are distant apart from eyes.
- Myopia is caused because of excessive curvature of the eye lens and elongation of the eye balls.
- To correct myopia the concave lens of proper focal length is used.
4.) When we enter a dark room from bright sunshine what happens with our eye and why?
Ans:
- When we are in the bright sunshine the more light enters our eyes which may harmful. Because of that, at that time the light entering is controlled by contracting the size of pupil due to which less and sufficient light enters into eyes.
- But, when we suddenly enters a dark room from bright sunshine that time because of contraction of pupil we can’t see the objects suddenly. But after sometime pupil starts expanding slowly so that more and sufficient light enters our eyes and hence we can see the objects in dark room also without any strain on our eyes.
5.) Which sensitive cells are present in the retina of our eye? And why we are not able to see objects in dark as clear as owl?
Ans:
- As we know that, the sensitive cells present in the retina of our eye are rods and cones.
- Rod cells are responsible for sensation of dim light while cone cells are responsible for bright light and colours of objects.
- The animals having night vision like owl which we called as nocturnal animals, they have rod cells in large amount in the retina of their eyes and hence they are able to see the objects in less light also.
- On the other side, in human being rod cells are present in less amount in retina and hence we cannot able to see objects in dark clearly.
6.) Give the difference between myopia and hypermetropia.
Ans:
Myopia:
- Myopia is also named as near sightedness or short sightedness.
- In myopic eye, person can see the nearby objects clearly but not able to see the objects which are at a larger distance clearly and distinctly.
- For myopic eye, the far point is found to be less than infinity.
- To correct myopia, concave lens are used.
- Because, concave lens reduces the converging power of eye lens and in that way forms the image of objects which are at larger distance on the retina of the person suffering from myopia.
Hypermetropia:
- Hypermetropia is also named as far sightedness or long sightedness.
- In hypermetropic eye, the person can see objects which are more distant apart but not able to see the objects which are close to our eyes or near to our eyes.
- For hypermetropic eye, the near point is more than 25cm away.
- To correct this defect convex lens are used.
- Because convex lens increases the converging power of eye lens and in that way forms the image of nearby or objects closed to our eyes on the retina.
7.) If a person is able to see objects clearly upto 1 meter only. Then which type of defect is that and how it is corrected?
Ans:
- Here, the person is able to see objects upto 1 meter only. That means he is able to see nearby objects only and not able to see distant objects.
- Hence, the person is suffering from myopia and to correct this defect concave lens of proper focal length can be used.
Here,
Image distance v = -1m
Object distance u = infinity
As we have,
1/f = 1/v – 1/u
1/f = -1/1 – 0
1/f = -1/1
f = -1m
Thus, power of lens is calculated as
P = 1/f = 1/-1= -1D
Hence, the person is suffering from myopia and it can be corrected by using concave lens of focal length 1m and power -1D.
8.) If a person is having near point at 30cm. Which type of defect is that and how it is corrected?
Ans:
- Here, the person is suffering from hypermetropia because he is able to see objects which are distant apart but not able to see nearby objects.
- This type of defect is corrected by using convex lens of proper focal length and power.
Here, from given
Image distance v = -30cm
Object distance u = -25cm
(Since, near point of normal eye is 25cm)
Now,
1/f = 1/v – 1/u
1/f = -1/30 + 1/25
1/f = 5/750
f= 750/5 = 150cm = 1.5m
Power of the lens is given as
P = 1/f = 1/1.5 = 0.66 D
Thus, here to correct the defect hypermetropia convex lens of power 0.66D is used.
9.) Explain presbyopia in detail.
Ans:
- Presbyopia is the eye defect which is mostly seen in the old persons, due to which they are not able to see objects closer to our eyes clearly.
- The person suffering from presbyopia loses the power of accomodation of their eyes.
- In case of old persons, ciliary muscles become weakened and due to loss of accomodation power of eye lens leads to make eye lens rigid.
- Sometimes presbyopia is corrected by using convex lens of proper focal length or bi focal lenses also.
10.) Why the colour of sky appears blue?
Ans:
- The blue colour of the sky is only due to the scattering of light.
- In scattering of light, the sunlight scatters from the small dust particles, air molecules which has very small size than wavelength of light.
- As we know that, the colours having short wavelengths scatters more, hence blue and violet light having shorter wavelength scatters more.
- So, blue and violet light scatters more in atmosphere but violet colour is that much not sensitive to our eyes and we can’t see it. Thus we can see only scattered blue light in atmosphere and hence sky appears blue to us.
11.) Why the sun appears red at sunrise and sunset?
Ans:
- As we know that, at the time of sunset or sunrise the sun located near to horizons because of that, the light rays coming from sun to reach earth that time needs to travel a longer distance.
- As we know blue and violet colour having shorter wavelength scatters more and spreads due to which they not reach on the earth. But red colour having longer wavelength scatters less and able to travel more distance and reaches to our eyes.
- Hence, sun appears reddish at the time of sunset or sunrise.
12.) How rainbow is formed?
Ans:
- After raining we can observe the sky becomes fully clear and hence clouds are on the opposite direction as that of the sun. Because of that sunlight becomes too bright.
- Also, after raining we can see some small tiny water droplets in the atmosphere and such tiny water droplets acts like a prism.
- When sunlight enters this droplets it gets splitted into seven coloured spectrum which we call as rainbow.
- Hence we can say rainbow is always formed on the opposite side of the sun’s position.
13.) Neha’s grandfather able to read the newspaper but can’t see the tv pictures clearly from far, why?
Ans:
- Here, grandfather is able to see nearby objects clearly but not able to see objects which are distant apart. That means grandfather is suffering from short sightedness or myopia.
- Thus defect can be corrected by using spectacles having concave lens of proper focal length and power.
14.) Why planets not twinkles like stars?
Ans:
- Stars are at larger distance and hence acts as a point source of light.
- While planets are somewhat near to earth’s surface and hence does not acts as a point source of light. Because of that they appears like huge source of light for human on the earth’s surface.
- As the plants acts as a huge source of light which is made up of large numbers of point source of light, the light coming from them on an average becomes zero or nullify and no light will reach to our eyes on the earth’s surface.
- Thus, as no light will reach to our eyes we can’t see planet as twinkling.
15.) Why astronaut can’t see sky as blue?
Ans:
- As the atmosphere on the earth’s surface contains large numbers of tiny particles, dust particles, air and water molecules and from these particles light gets scattered and most scattered light colour is blue and we see sky as blue.
- But for astronaut in the space no such particles are present because there no atmosphere and hence no scattering will happen and hence they see sky as dark only not any coloured or blue.
Long Answer Questions:
1.) Explain short sightedness with diagram. And draw diagram of corrected defect also.
Ans:
- As we know, myopia is called as short sightedness.
- Person suffering from myopia can see nearby objects clearly but cannot see objects which are distant apart.
- The main cause of myopia is increase in converging power of eye lens or we can say eye balls get elongated.
- The diagram given below shows myopic eye or short sightedness.
- To correct myopia concave lens of proper focal length and power is used so that it diverge the rays coming from distant objects and forms the image exactly on the retina of our eye.
- The diagram given below shows correction for myopic eye using concave lens.
2.) Explain far sightedness with diagram. And draw diagram of corrected defect also.
Ans:
- As we know that, hypermetropia is also called as long or far sightedness.
- The person suffering from hypermetropia can see the objects which are distant apart but cannot see nearby objects clearly.
- The main cause of hypermetropia is the low converging power of eye lens or we can say it as shortening of eye balls.
- The diagram given below shows hypermetropic eye.
- To correct hypermetropia convex lens of proper focal length and power is used so that it converge the rays coming from nearby objects and forms the image exactly on the retina of our eye.
- The diagram given below shows correction for hypermetropic eye using concave lens.
3.) Draw the well labelled diagram of human eye.
And give the functions of following parts of eyes.
- a) pupil
- b) eye lens
- c) ciliary muscles
Ans:
The following is the well labelled diagram of human eye.
a) pupil:
The function of pupil in human eye is to control the amount of light entering by changing the size of the pupil.
b) eye lens:
With the help of pupil light enters in our eyes and it is converged with the help of eye lens and focused on the retina so that image produced will be real and inverted.
c) ciliary muscles:
Ciliary muscles helps in changing the focal length of the eye lens.