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Kerala State Syllabus 10th Standard Physics Solutions Chapter 6 Vision and the World of Colours
Vision and the World of Colours Textual Questions And Answers
Text Book Page No. 133
Vision and the world of Colours Question 1. Place a lighted candle at a distance 13 cm from the lens. Do you get a clear image of the candle on the screen?
Physics of Vision Question 2. Place lenses of focal length 10 cm, 15cm and 20cm on the lens holder without changing the distance between the lens and the screen. On using which lens is the image clear?
Lens of focal length 10 cm
Text Book Page No. 134
Given below are the ray diagrams of image formation in the eye.
i. Where is the image formed in each case?
ii. In which case is the image formed on the retina itself ?
(i) a) In front of retina
b) Behind the retina
c) On retina
World of Vision Question 4. Will an image be formed on the retina when the object is at the near point
Will it be possible to see a clear image?
No. It will not be possible to see a clear image.
Textbook Page No. 135
Will an image be formed on the retina when the object is at a far distance
Will a clear image be formed?
Yes. A clear image will be formed.
What shall be the reasons behind this defect?
1. Can you find out a reason based on the size of the eyeball?
Size larger/ smaller?
2. What if it is related to the focal length (or power)?
Power is high/ low
What is the remedy for long – sight-edness?
This can be rectified by using a convex lens of suitable power.
Text Book Page No. 136
Where is the image formed in these cases? Write down the answer analysing.
1. When the object at O is away from the eye, where will be the image formed? Can the object be seen clearly?
In front of retina. Objects cann’t be seen clearly.
2. Can the object be seen clearly when it is at O1?
3. Why is it not possible to see objects placed at long distances?
dmages are formed in front of retina.
4. What is its remedy?
This can be overcome by using concave lens of suitable power.
Physics Chapter 6 Question 9. When a person suffering from problem in vision met a doctor, he wrote in his prescription the following figures. +1.5 D, -2D
1. What has the doctor indicated in the prescription?
+1.5 D, -2D indicates the power of lense they required. The power of a lens is defined as the ability of the lens to converge or diverge a beam of light falling on it.
2. Which are the types of lenses prescribed here?
The power of a convex lens is positive while the power of a concave lens is neg-ative.
+1.5D represents convex lense.
-2D represents concave lense.
For a healthy vision, what is the dis-tance to the near point?
Text Book Page No. 137
Pass sunlight through a prism and allow it to fall on a screen. What are the colours seen on the screen?
Violet, Indigo, Blue, Green, Yellow, Orange, Red.
Text Book Page No. 138
Formation of Rainbow Class 10 Question 12. The beam of white light from a torch is allowed to fall obliquely on the prism.
1. Which are the colours formed on the screen?
Violet, Indigo, Blue, Green, Yellow, Orange, Red.
2. Aren’t these colours the same as the component colours obtained from the sunlight?
1. Which colour deviates the most due to dispersion?
2. Which colour deviates at least?
3. What may be the reason behind this difference in deviation?
Differences in wavelength
1. Which colour has the shortest wavelength?
2. Which one has the longest?
When light passes through the prism, as the wavelength increases, how does the deviation change? Will it increase or decrease?
The deviation of colours is minimum for the colours with more wavelength when the composite light passes through the prism. When the wavelength of the colour decreases, the deviation increases.
Text Book Page No. 139
When is the rainbow formed?
In the morning and in the evening.
Where will be the sun when the rainbow is seen in the east?
In the opposite direction (west)
Where will be the sun when the rainbow is seen in the west?
How many times does a ray of light undergo refraction when it passes through a water droplet?
The sunlight undergoes two times refraction in the water drop.
What about internal reflection?
What is the colour seen at the upper edge of the rainbow?
What is the colour seen at the lower edge?
Text Book Page No. 140
What happened to the light when it passed through the first prism?
The white light separates into its component colours when it passes through the first prism
What happened when it passed through the second one?
The colours formed by the first prism recombine to form white light when it passes through the second prism.
Text Book Page No. 141
Make a Newton’s disc by painting the constituent colours of white col-our of white light in the same order and proportion.
In which colour does the disc appear when rotated fast?
Very near to the white colour
Light from the seven colours of the colour disc falls continuously on the retina and due to the persistence of vision, disc appears as white.
The disc appeared white due to persistence of vision. Find out more examples of persistence of vision and write them down.
- A torch rotated rapidly appears as an illuminated circle.
- Sparkler’s trail effect.
- Colour – top
- Kaleidoscopic colour-top.
- Rubber pencil trick.
- LED POV displays
- Revolving wheels,
- Rotation of fan leafs
During sunset, you might have no- I ticed that the western horizon becomes reddish. Why is it so?
During sunset, the sunlight travels I maximum distance through the atmosphere to reach in our eyes. So red also I undergo scattering. So the horizon appears red.
Text Book Page No. 142
Is the reflection of light here regular or irregular?
Is the distribution of sunlight to all regions made possible by this type of scattering. Discuss.
Yes, scattering is the partial and irregular reflection of light. The colours in sunlight undergo scattering when they fall on the particles in the atmosphere. Sunlight reaches in the rooms and under the trees by this method.
Text Book Page No. 143
When hydrochloric acid was added to the solution, which colour did spread first in the solution?
Blue colour spreads first in the solution when acid was added.
Write down the colour changes observed on the screen in the order it occurred.
Violet → indigo
blue → green → yellow
orange → red
What was the final colour observed on the screen?
Red colour is seen at the end.
Which component colour in white light does undergo maximum scattering?
Blue has the maximum scattering
During sunset, the horizon appears to have red colour. What may be the reason?
During sunrise and sunset, light reaching us from the horizon has to travel long distances through the atmosphere. During this long journey, colours of shorter wavelength would be almost fully lost due to scattering. Then, the red light which undergoes only less amount of scattering decides the colour of the horizon. That is why the sun appears red during sunset and sunrise.
Text Book Page No. 144
Which are the occasions when sun-light has to travel greater distance through the atmosphere before reaching the eyes of ait observer on the earth?
Morning and evening.
As sunlight passes through the atmosphere, which colour in it undergoes maximum scattering? Which colour undergoes minimum scattering?
Colour in it undergoes maximum scattering: Violet
Colour in it undergoes minimum scattering: Red
When light reaches the observer after travelling long distances through the atmosphere, which colour reaches the eye? What is the reason?
Red, it has highest wavelength and least scattering.
The western horizon remains reddish for some more time even after sunset. Why?
During sunset, the sunlight travels maximum distance through the atmosphere to reach in our eyes. So red also undergoes scattering. So the horizon appears red.
Can you now guess why red colour has been given to the tail lamps of vehicles and signal lights? Discuss and note it down in your science diary.
The primary reason why the colour red is used for danger signals is that red light is scattered the least by air molecules. So red light is able to travel the longest distance through fog, rain, and the like.
Text Book Pace No. 145
Write down what else can be ‘done to minimize the light pollution.
- Start with the light switch
- Check with your power company to see if you’re paying for outdoor lighting.
- Consider replacing outdoor lights with intelligently designed, low- glare fixtures.
- Place motion sensors on essential outdoor lamps.
- Replace conventional high-energy bulbs with efficient outdoor CFLs and LED floodlights.
- Reduce the use decorative lighting.
- Use of covered bulbs that light facing downwards.
- The use of automatic systems to turn off street light at certain times.
- Have all information arid facts about light pollution.
- Use of glare-free bulbs, installing low hanging bulbs, having the lights facing downwards, and covering the bulbs to reduce bright skies at night.
- Share with family and friends.
Let Us Assess
How is the condition of the ciliary muscles while watching a distant object? How does this influence the focal length of the eye lens?
While looking at far objects the ciliary muscles are relaxed and the curvature of the lens decreases. The focal length of the lens increases.
A child sitting at the backbench of a classroom is unable to see the letters on the board clearly. What is the defect of the eye of the child? How can it be remedied? Draw its ray diagram.
Myopia or Nearsightedness. This can be rectified by using a concave lens of suitable power.
A person is not able to see objects beyond 1.3 m. What remedy can you suggest for this defect?
Myopia or Nearsightedness. This can be rectified by using a concave lens of suitable power.
In what colour does the sky appear for an astronaut?
Red light is used as signal lamps to indicate danger. Explain.
The primary reason why the colour red is used for danger signals is that red light is scattered the least by air molecules. So red light is able to travel the longest distance through fog, rain, and the a like.
What is the reason for using yellow light as fog lamps?
Yellow lights are strictly used for fog situations, and for construction, so you can tell what is what on the road. Yellow has high wavelength, so yellow light is scattered the least by air molecules.
Which is the phenomenon behind dispersion of light?
c. Tyndal Effect
During dispersion, different colours deviate differently. Explain why.
The rate of refraction for different col-ours during dispersion is different due to the difference in wavelength of the colours. The rate of refraction decreases with increase in wavelength. Dispersion. is the phenomenon of splitting of light into its component colours.
The telescope called ‘Chandra X-ray Observatory’ is placed in the outer space. What is the advantage of placing it there? Explain with reference to the scattering of light in the atmosphere.
Light can reach the telescope which is kept in space without scattering as there are no gases and tiny particles in space. So we can observe the heavenly bodies clearly there. The pictures may not be clear on earth due to the scattering of light.
White light is allowed to fall on the bright side of a compact disc (CD). The reflected light is allowed to fall on a white wall. Observe the colours available in the spectrum and write them down in your science diary.
Violet, indigo, blue, green, yellow, Orange, Red.
Vision and the World of Colours Orukkam Questions and Answers
Observe the figure
a. Which are the colours formed on the sc-reen?
b. Explain the phenomenon that causes the formation of array of colours
c. Which are the colours denoted by ‘A’ and ‘B’?
d. Which colour deviates the most?
e. Which colour deviates at least?
f. Different colours undergo different deviation. Why?
a. Violet, Indigo, Blue, Green, Yellow, Orange, Red
b. Dispersion. The phenomenon of splitting, of a composite light into its constituent colours is known as dispersion of light.
c. A – Violet B – Red
f. Different colours undergo different deviation due to difference in wavelength
Newton’s colour disc is made by painting the constituent colours of white light in the same order and proportion.
a. In which colour does the disc appear when rotated fast?
b. The reason behind such an appearance is a phenomenon related to our eyes. What is it explain?
c. If the disc is rotated slowly, what will be the observation?
d. Why does a torch rotated appear as an illuminated circle?
a. White colour
b. Persistence of vision. When a person views an object, its image remains in the retina of the eye for a time interval of 0.0625 s
c. If the disc is rotated slowly it is easy to identify the different colours.
d. Due to the Persistence of vision.
The figure shows a ray of sunlight falls obliquely on a water drop.
a. Complete the figure
b. How many times does the ray of light undergo refraction?
c. A natural phenomenon is there that connected with this figure. Name it?
Match columns. A, B and C suitably.
|Colour of light||Complementary colour||Colour obtained|
|Green||……. (a) ……||White light|
|Yellow||Blue||…… (b) ……|
|Red||……. (d) ……||White light|
b. White light
The telescope ‘Chandra’ is placed in the space. What is the advantage of placing it there?
Light can reach the telescope which is kept in space without scattering as there are no gases and tiny particles in space. So we can observe the heavenly bodies clearly there. The pictures may not be clear on. earth due to the scattering of light.
Vision and the World of Colours SCERT Questions and Answers
The figure shows a ray of light falling obliquely on a droplet of water for the formation of rainbow.
a. Copy the figure and complete the unfinished part.
b. What is the phenomenon that took place inside the droplet?
c. What is the colour of ‘X’?
d. What is the reason behind the red app-earing at the outer edge of a rainbow?
b. Internal reflection
d. Sunlight undergoes refraction and internal reflection while passing through drops of water. All the drops that appear in the same colour are seen in the same arc. Thus red having highter wavelength is seen in the outer edge at higher angle.
Analyse the following statements and find out the reason behind them.
a. Stars can be seen even in day time while viewed from the moon
b. Raindrops falling down during rain appear like a glass rod.
c. A rainbow is seen in the shape of a circle when viewed from a height.
d. The sky of cities mostly appears in grey colour.
a. There is no scattering for the light around the moon since there is no atmosphere around it. Hence the sky of moon appears dark.
b. Raindrops come down faster during rain. The distance travelled by a drop in 1/16 of a second appears like a glass rod due to persistence of vision.
c. When viewed from a height the observer can see points at 42.70 upwards, downwards as well as sideways. Hence rainbow is seen as a circle.
d. In cities there will be large particles in the atmosphere. Hence all colours of light scatter equally.
Two teams A and Bare taking part in a volley ball competition held on a ground illuminated by a sodium vapour lamp (yellow light). Team A is wearing white jersey and blue shorts while Team B is wearing yellow jersey and black shorts.
a. Can you distinguish between the teams based on the colour of their dress?
b. Justify your answer.
a. Cannot be distinguished
b. In yellow light the white jersey and yell-ow jersey appear in yellow colour. This is because both white and yellow surfaces can reflect yellow light. The black shorts appears black itself and blue shorts appears dark since both of them absorb yellow light.
A disc painted with different colours is shown
a. Which colour is X if the disc appears white on rotating fast?
b. Why did the disc appear white on being rotated fast?
c. In what colour will the disc appear if green light alone is made to fall on the disc when it is being rotated fast?
b. Due to persistence of vision
c. In green colour
On rotating the disc faster, the disc app-ears white due to persistence of vision. The cyan appears as green since it reflects green light.
Colour filters are materials that will allow only certain colours of light to pass.
a. What is the colour of the filter that can transmit blue and red colours of light?
b. Which are the radiations that will be absorbed completely by an infrared filter?
c. Write down:
(i) Two specialities of infrared rays
(ii) Two uses of infrared rays
b. Visible light, ultra violet radiations
c. (i) Higher wavelength than that of visible light; becomes the reason for the heat . of the sunlight.
(ii) Used to take photograph of distant objects, remote sensing, secret signalling, for controlling robots.
The figure shows sunlight falling on a white screen after being passed through yellow and cyan filters.
a. Supply the omitted portion and complete the diagram
b. Which colours is‘X’?
c. (i) What is the complementary colour of this colour?
(ii) What do you mean by complementary colours?
c. (i) Magenta
(ii) If a primary colour and a secondary colour can given white light on mixi-ng, then they are complementary colours.
Match the columns A, B and C suitably
|Light makes tiny particles visible due to scattering||Dispersion||Pictures on a TV screen keep on changing and give an illusion of motion.|
|The effect of seeing an object is retained by the eye for 1/16 of a second.||Tyndal Effect||Formation of rainbow on the horizon|
|Composite light splits up into component colours||Persistence of vision||On foggy morning the path of sunlight becomes clearly visible. ‘|
|Light makes tiny particles visible due to scattering||Tyndal Effect||The path of sunlight becomes visible foggy mornings.|
|The effect of seeing an object is retained by the eye for 1/16 of a second.||Persistence of vision||The pictures of a TV screen continuously change giving the Illusion effect of motion of them|
|Composite light splits up into component colours||Dispersion||Rainbow appears on the horizon|
A spectrum is obtained by passing white light from a torch through a glass prism.
a. Write down the steps of this experiment.
b. Draw a figure that represents the experiment.
a. Fix a black paper in from of a torch. Put a small hole in the middle of the paper. Arrange a screen on the other side. Make the beam of light fall obliquely on the prism.
The telescope ‘Chandra’ is installed on the outer space. Identify the correct statements related to it.
a. There is no scattering of light in the outer space
b. There is a greater scattering in the outer space
c. The vision is more accurate and clear
d. Presence of dust in the outer space helps in better vision and clarity
Correct statements: a and c
Which of the following does not belong to the group?
a. red, yellow, blue, green
b. visible light, sound, X-rays, radio waves
a. Yellow – it is a secondary colour
The rest are primary colours
b. Sound- it is a mechanical wave The rest are electromagnetic waves
Find out the relation between the first pair and complete the other accordingly:
a. Black: absorbs all colours of light white:
a. Reflects all colours of light.
Vision and the World of Colours Exam Oriented Questions and Answers
Very Short Answer Type Questions (Score 1)
Find the odd one in the group and write the reason. [Red, Green, Blue, Yellow]
Yellow. Others are primary colours
Using the relation from the first pair, complete the other.
Tyndal effect – scattering
Dispersion – ………………
Which of the following causes skin cancer,
What is the colour seen at the inner edge of a rainbow?
Fill in the blanks.
Green + ………. = Yellow
What is the change in the deviation of those rays having lesser wavelength compared to those rays having higher wavelength? (more, less, no change)
Name the phenomenon responsible for dispersion of light.
In the given figure which is correct.
Distance to the near point of a healthy person is? (10 cm, 50 cm, 100 cm, 25 cm)
Short Answer Type Questions (Score 2)
Arrange the following colours in the in-creasing “order of their wavelengths.
Violet, Red, Green, Blue
Violet, Blue, Green, Red
Yellow light from a torch falls on a green paper and then falls on a white screen.
a. Which colour is seen on the screen?
b. Write the reason in two or three sentences.
a. Green colour
b. When yellow light falls on a green paper it absorbs yellow and reflects green. So . the green colour is seen on the screen.
Myopia and Hypermetropia are the eye defect of human beings, identify the given statement then separate the reason for Myopia and Hypermetropia.
a. Image is formed behind the retina
b. Images formed in front of the retina
c. Power of the eye lens decreases
d. Power of the eye lens increases
e. Suitable power of concave lens is used to solve this problem
f. Suitable power of convex lens is used to solve this problem
Myopia -b, d, e
Hypermetropia -a, c, f
Why concave lens always create virtual and erect image of the object?
In this case, refracted Ray do not actually intersect to each other. It appears to intersect the images formed the same side of the lens.
Short Answer Type Questions (Score 3)
a. Complete the ray diagrams in the figures A and B when the rays of light passes through the prisms and reach out of them with the changes occurred to them.
b. If there are differences between the figures explain the reason
b. There is only one colour in laser. Sunlight is the composite light of seven colours and so undergoes refraction
Explain the reason for the following.
a. At the time of sunset, western horizon is seen red.
b. Sky in the moon ha» a dark colour
a. At the time of sunset, Light rays have to travel very long distances through air. Hence Light rays are scattered. Light rays like blue with shorter wavelength get lost due to scattering but rays with longer wavelength remain because it gets less scattering.
b. In moon there is no atmosphere and therefore scattering of light does not take place.
The figure shows a ray of light falling obliquely on a drop of water in atmosphere
a. Copy the diagram and complete it show-ing the internal reflection and refractions.
b. How does the sunlight appear as rainbow in water droplets?
b. All the water droplets of the same colour appear to be in a same arc of a circle. The rays of light incident on the water droplets must be parallel to the line of vision. Each colour ray emerging from the water drop makes a definite angle from 40.8° to 42.7°. Red makes the higher angle of 42.7° and violet ma-kes a lower angle of 40.8°. Hence red colour is seen at the outer edge and violet colour at the inner edge. The other colours are seen in between depending on their wavelengths.
The image formation of a defected eye is given below
a. In which position images formed on a normal eye?
b. What is this eye defect?
c. How to solve this defect? Draw the diagram.
a. On the retina.
c. Suitable power of concave lenses is used to solve this problem.
Short Answer Type Questions (Score 4)
Find the appropriate terms from the box for the statements given below.
Red, Scattering, Refraction, Dispersion
a. Phenomenon responsible for Rainbow.
b. Phenomenon responsible for Tyndal effect.
c. Colour seen at the outer edge of the rainbow.
d. Phenomenon responsible for Dispersion of Light.
Rearrange the table given below correctly.
|Dispersion||More Wavelength||Green colour|
|White colour||Tiny particles||Used in remote controls|
|Scattering||Less wavelength||Vitamin D|
|Infrared ‘||Magenta colour||Sunlight|
|Ultraviolet||White colour||Visible spectrum|
|Dispersion||White colour||Visible spectrum|
|White colour||Magenta colour||Green colour|
|Infrared||More Wavelength||Used in remote controls|
|Ultraviolet||Less wavelength||Vitamin D|
Analyse the picture and answer the questions.
a. What is the colour of the light falling on the white screen?
b. What colour is obtained on the screen if blue filter is used instead of green filter?
b. When blue filter paper is used, no light will fall on the screen. The yellow, green and red colours coming out of the yellow filter will not pass through blue filter paper.
When Newton’s colour disc rotates fast it appears white.
a. Which phenomenon is responsible for this?
b. Define this phenomenon.
c. Write another example related to this phenomenon.
a. Persistence of Vision.
b. When an object is viewed by a person, the image remains in the retina for a time interval of 1/16 second. This phenomenon is called persistence of vision.
c. Raindrops look like glass rods during rain.