Class 10 Physics Chapter 3 Important Questions Kerala Syllabus The World of Colours and Vision

The comprehensive approach in SCERT Class 10 Physics Solutions Chapter 3 The World of Colours and Vision Important Questions with Answers ensure conceptual clarity.

SSLC Physics Chapter 3 Important Questions Kerala Syllabus

The World of Colours and Vision Class 10 Important Questions

Question 1.
Find the odd one
a) Red, green, magenta, blue
b) magenta, yellow, cyan, green
Answer:
a) Magenta. (It is a secondary colour)
b) Green. (It is a primary colour)

Question 2.
Red, green and blue are called ………………….
Answer:
Primary colours.

Question 3.
………………… light is the combination of two primary colours of light.
Answer:
Secondary

Question 4.
What are complementary colours?
Answer:
When a secondary colour is combined with a primary colour, we get white light. Such pairs of colours are called complementary colours.

Question 5.
Which of the following statements is / are correct?
a) A surface that reflects all colours will appear dark in white light.
b) A surface that absorbs all colours appears dark.
c) A surface that reflects all colours will appear white in white light.
Answer:
c) A surface that reflects all colours will appear white in white light.

Question 6.
Find the relation between the first word pair and complete the second pair.
Blue : Primary colour
Cyan : ………………
Answer:
Secondary colour

Question 7.
The ………………… radiation in the sunlight is the main reason for the heat in the Sun’s rays.
Answer:
Infrared

Question 8.
Light composed of different colours is called …………………
Answer:
Composite light

Question 9
…………………. is the phenomenon of splitting up of a composite light into its component colours.
Answer:
Dispersion of light

Question 10.
Why Red light is used in signal lamps and tail lamps of vehicles?
Answer:
Red light is used in signal lamps and tail lamps of vehicles because red undergoes least scattering due to its greater wavelength.

Question 11.
In what colour does the sky appear for an astronaut?
Answer:
Black/Dark

Question 12.
What is the reason for using yellow light as fog lamps?
Answer:
Yellow has comparatively greater wavelength and low scattering. Moreover it has more visibility.

Question 13.
Which is the phenomenon behind dispersion of light?
a) Reflection
b) Refraction
c) Tyndal Effect
d) Scattering
Answer:
b) Refraction

Question 14.
During dispersion, different colours deviate differently. Explain why.
Answer:
Due to the difference in wavelength.

Question 15.
The telescope called ‘Chandra X ray Observatory’ is placed in the outerspace. What is the advantage of placing it there? Explain with reference to the scattering of light in the atmosphere.
Answer:
In the outerspace, there is no atmosphere and scattering of light does not take place. So clear images can be captured.

Question 16.
Find the relation between the first word pair and complete the second pair.
Persistence of hearing : 1/10 second
Persistence of vision : ……………………
Answer:
1/16 second

Question 17.
Which is the correct figure?

Answer:
Figure 2.

Question 18.
Write down the phenomena behind the following.
Formation of Rainbow: ………………….
Tyndal effect: …………………..
Answer:
Dispersion
Scattering

Question 19.
Find the relation between the first word pair and complete the second pair.
Long Sightedness: Convex lens
Presbyopia: …………………..
Answer:
Convex lens

Question 20.
a) In which case is the image formed on the retina itself?

b) In the other cases, the image is not formed on the retina. Why?
Answer:
a) In (c)
Change in the power of the lens of the eye.
Change of the size of the eye ball.

Question 21.
a) What are the reasons behind long-sightedness?
b) What is the remedy for this defect?
Answer:
a) The size of the eyeball is smaller.
The power of the lens is less.
b) This can be rectified by using a convex lens of suitable power.

Question 22.
Complete the table

Secondary colour	Complementary colour
Yellow ….(b)…. Cyan	….(a)…. Green ….(c)….

Answer:
a) Blue
b) Magenta
c) Red

Question 23.
Write two examples of persistence of vision.

• A torch rotated rapidly appear as an illuminated circle.
• When a burning incense stick is whirled very fast, a ring of fire can be seen.

Question 24.
Explain what is meant by Tyndal effect?
Answer:
When light rays pass through a colloidal fluid or suspension, the tiny particles get illuminated due to scattering. Due to this the path of light is made visible. This phenomenon is known as Tyndal effect.

Question 25.
a) What is the relation between the deviation of component colours of white light through a prism and their wavelength?
b) Classify the colours green, red, indigo and yellow in the descending order of their wavelengths.
Answer:
a) When wavelength increases deviation decreases. When wavelength decreases deviation increases.
b) Red, yellow, green, Indigo.

Question 26.
Roshan observed a beautiful rainbow in the western sky from his school ground.
a) When did Roshan observe the rainbow? [Morning, Noon, Evening, Prediction of time is impossible]
b) Draw the diagram of dispersion taking place in a water droplet during the formation of a rainbow.
Answer:
a) Morning.
b)

Question 27.
To get clear vision, the images of near object and distant object should fall on the retina of the eye.
a) Name the ability of eyes to get an image on the retina.
b) How does eyes adjust itself to get the image of distant object on the retina?
Answer:
a) Power of accommodation.
b) When we view distant object the ciliary muscles are relaxed and the curvature of the lens decreases. Then focal length of eye lens increases.

Question 28.
An ophthalmologist gave prescription to a patient to buy spectacles. It is written as + 1.25 and -1.5 D.
a) What has the doctor indicated in the prescription.
b) What are the type of lenses prescribed above?
Answer:
a) Power of lens used in the spectacle.
b) + 1.25D : Convex lens.
-1.5D : Concave lens.

Question 29.
The sun’s rays entering a glass prism is shown in the figure given below.

Copy the image and mark the colours by depicting the light falling on the screen.
Answer:

Violet, indigo, blue, green, yellow, orange, red colours are the colours falling on the screen.

Question 30.
a) Observe the images related to image formation in the eyes

b) What are the reasons behind near-sightedness?
c) What is the remedy for this defect?
Answer:
a) B
b) The size of the eye ball is larger.
The focal length of the eye lens is low (power high)
c) This can be overcome by using concave lens of suitable power.

Question 31.
Give reasons
a) When light passes through a suspension, the light path can be clearly seen.
b) The sky appears blue.
c) The sun appears red, yellow, or orange during sunrise and sunset.
Answer:
a) When light passes through a suspension, the light path can be clearly seen due to scattering,

b) When sunlight travels through the atmosphere to reach the Earth, some of its components undergo scattering as it passes through the air. Scattering occurs most for colours with shorter
wavelengths such as violet, indigo and blue. This scattered light spreads in the sky. The resultant scattered light that reaches the observer’s eye gives the effect of the blue colour. So the sky appears blue.

c) The sun appears red, yellow, or orange during sunrise and sunset because its light travels through more of the Earth’s atmosphere. As it does, the shorter blue wavelengths scatter more, leaving the longer wavelengths (red, or-ange, and yellow) for us to see.

Question 32.
Describe an experiment to know’ whether all the colours of sunlight undergo similar type of scattering.

Water is taken in a beaker as shown in figure. Allow light from a torch to fall on the water from one side of the beaker. The light emerging from the beaker is focussed on a white screen. Sodium thiosulphate is dissolved in water in the beaker at the rate of 2 g per litre. Add one or two drops of hydrochloric acid to the water in the beaker.

When sodium thiosulphate and hydrochloric acid react, colloidal sulphur is precipitated. The size of the particles gradually increases. Blue colour spreads first in the solution and Red is the last colour to appear on the screen.

Question 33.
Observe the figure given below and answer the following

a) Which are the occasions when sunlight has to travel greater distance through the atmosphere before reaching the eyes of an observer on the earth?
b) When light reaches the observer after travelling long distances through the atmosphere, which colour reaches the eye? What is the reason?
c) Even after sunset, the western horizon continues to have red colour for some more time. Why?
Answer:
a) In the morning and in the evening sunlight has to travel greater distance.
b) Red. Because it possess greater wavelength.
c) During long distant travelling of sunlight, colours of shorter wavelength would be almost fully lost due to scattering and only red will predominate.

Question 34.
What will be the consequences of light pollution?
Answer:

• Causes difficulty during night drive.
• Makes astronomical observations difficult by obstructing the night sky.
• The light from multi-storeyed flats misleads migratory birds.
• It adversely affects the breeding and predation of many nocturnal species.

Question 35.
WhenNewton’s colour disc rotates fast it appears white.
a) Mention the phenomenon related to this?
b) Define this phenomenon.
c) Write another example related to this?
Answer:
a) Persistence of vision.
b) When a person sees an object, its image remains in the retina for a time interval of a 1/16 second. This phenomenon is called persistence of vision.
c) When a burning incense stick is whirled very fast, a ring of fire can be seen.

Question 36.
Describe an experimental set up to show that sunlight can be split up into constituent colours and then convert it back to white light.
Answer:
Allow sunlight to fall on the white wall using a plane mirror and a slit. Place a triangular prism in the path of the light. We can see seven colours falling on the wall due to dispersion of light. Place another prism in such a way that the constituent colours pass through the second prism. We can see white light again.

Question 37.
a) How is the deviation of white light into its constituent colours related to its wave length?
b) Write the colours Green, Red, and Indigo in the order of decreasing wavelength.
c) Sun light and laser beam are incident obliquely on an equilateral glass prism.
Represent diagrammatically what happens to the beam in the laser.
Answer:
a) As wavelength increases, deviation decreases and as wavelength decreases deviation increases.
b) Red > Green > Indigo
c)

Question 38.
a) What is the name of the nearest point at which the object can be seen distinctly?
b) What is the least distance of distinct vision for a healthy eye?
c) What is the farthest point at which objects can be seen clearly?
d) What is the longest distance for healthy vision of an eye?
e) What is the relation between curvature and focal length of a lens.
f) Name the part of the eye which helps to vary the curvature of the eye lens.
g) What is power of accommodation?
Answer:
a) Near point
b) 25 cm
c) far point
d) Infinity
e) They are inversly proportional
f) Ciliary muscle
g) The ability of the eye to form an image on the retina by adjusting the focal length of the lens in the eye, by varying the curvature of the lens, irrespective of the position of the object is the power of accommodation.

Question 39.
Match the columns A, B and C suitably.

A	B	C
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 mornings the path of sunlight becomes clearly visible.

Answer:

A	B	C
Light makes tiny particles visible due to scattering.	Tyndal Effect	On foggy mornings the path of sunlight becomes clearly visible.
The effect of seeing an object is retained by the eye for 1/16 of a second.	Persistence of vision	Pictures on a TV screen keep on changing and give an illusion of motion.
Composite light splits up into component colours.	Dispersion	Formation of rainbow on the horizon.

Question 40.
Answers to the questions based on the figure given below.

a) Which colour deviates the most due to dispersion?
b) Which colour deviates least?
c) Which colour has the shortest wavelength?
d) Which one has the longest
e) When light is passed through a prism, as the wavelength increases how does the deviation change? Will it increase or decrease?
Answer:
a) Violet undergoes most deviation.
b) Red undergoes least deviation.
c) Violet has the shortest wavelength.
d) Red has the longest wavelength.
e) As the wavelength increases the deviation decreases. As the wavelength decreases the deviation increases.

Question 41.
Answers to questions based on the figure given below.

a) How many times does a ray of light undergo refraction when it passes through a water droplet?
b) What about the internal reflection?
c) What are the colours seen at the outer edge of the rainbow?
d) What are the colours seen at the inner edge?
Answer:
a) Light ray undergoes refraction two times.
b) It undergoes internal reflection one time.
c) Red
d) Violet

Question 42.
Complete the table suitably

Filter	Light falling on the filter	Transmits/Does not transmit
Yellow	Red
	Green
	Blue
	Magenta
	White

Answer:

Filter	Light falling on the filter	Transmits/Does not transmit
Yellow	Red	Transmits red
	Green	Transmits green
	Blue	Does not transmits blue
	Magenta	Transmits red
	White	Does not transmits red, blue, yellow

Question 43.
Complete the table suitably

Filter	Light falling on the filter	Transmits/Does not transmit
Cyan	Red
	Green
	Blue
	Magenta
	White

Answer:

Filter	Light falling on the filter	Transmits/Does not transmit
Cyan	Red	Transmits/ Does not transmit
	Green	Does not transmits red
	Blue	Transmits green
	Magenta	Transmits blue
	White	Transmits blue

Question 44.
Blue colour of sky is due to the phenomenon of scattering
a) What is meant by scattering b
b) How is Tyndal effect related to above phenomenon?
c) What are the advantage of using infrared photography?
d) In which colour does sky appear when viewed from moon?
Answer:
a) Scattering is the irregular and partial directional deviation of light when it encounters particles in a medium.

b) When light rays pass through a colloidal liquid or suspension, they get scattered, causing tiny particles to become illuminated, making the path of light visible. This phenomenon is the Tyndall effect.

c) To take clear photographs of distant objects.

d) The sky is seen dark.

Question 45.
Our eyes play an important role in our vision.
a) Which part of the eye helps the image to fall on the retina as the position of the object changes?
b) The lines of a newspaper held at a distance of 10 cm from the eye are not clearly visible. Why?
c) If the doctor’s prescription for spectacles for a person with visual impairment is written as -2D, what type of lens is mentioned in the prescription? What could be the defect of his eye?
d) Name an eye defect that is characterized by less power of accomodation.
Answer:
a) Ciliary muscles.
b) For healthy eyes, the minimum distance for clear vision is 25 cm.
c) Concave lens, Myopia
d) Presbyopia

Question 46.
What phenomenon causes light to bend when it enters a prism?
Answer:
Refraction of light

Question 47.
What happens to light when it leaves the prism?
Answer:
The light bends again and changes direction.

Question 48.
What are electromagnetic radiations?
Answer:
Visible light, infrared radiation, ultraviolet radiation do not require a medium to travel. They travel through vacuum at a speed of 300,000 kilometre per second (3 × 10⁸ m/s). Such radiations are electromagnetic radiations.

Question 49.
Differentiate between primary colours of light and secondary colours of light?
Answer:
With red, green and blue lights, we can create not only white light, but also all other colours of light. So, these colours are called primary colours.
The coloured light formed by combining any two primary colours is a secondary colour of light.
Eg: Yellow, magenta, cyan.

Question 50.
Take a circular disc. Colour half of it with light magenta colour and the other half with light green colour using crayons. Rotate this circular disc very fast. What do you observe? Why?
Answer:
The circular disc appears white due to persistence of vision. When complementary colour pairs are combined we get white light.

Question 51.
What is the relation between scattering and wave length?
Answer:
As the size of the particle increases, the rate of scattering also increases. If the size of the particle is greater than the wavelength of light then the scattering is same for all colours.

Question 52.
Which component colour in white light does undergo:
a) maximum scattering?
b) minimum scattering?
Answer:
a) Violet having less wavelength undergoes maximum scattering.
b) Red having more wavelength undergoes least scattering.

Question 53.
Observe the figure

a) Which are the colours formed on the screen?
b) Explain the phenomenon that causes the formation of array of colours.
c) Which are the colours denoted by ‘A’ and ‘B’?
Answer:
a) VIBGYOR
b) Dispersion
c) A – Violet, B – Red

Question 54.
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.
c) If the disc is rotated slowly, what will be the observation?
Answer:
a) White
b) Persistence of vision
c) It does not appear white

Question 55.
Elderly people read newspaper by holding it at a distance than usual.
a) Name the defect of the eye behind this.
b) Which type of lens is used to correct their defect?
Answer:
a) Presbyopia
b) Convex lens

Question 56.
Match the following

A	B
Near point	Concave lens
Far point	25 cm
Myopia	Convex lens
Hypermetropia	Infinity

Answer:

A	B
Near point	25 cm
Far point	Infinity
Myopia	Concave lens
Hypermetropia	Convex lens

Question 57.
How is the condition of the ciliary muscles while watching a distant object? How does this influence the focal length of the eye lens?
Answer:
While looking at far objects the ciliary muscles are relaxed and the curvature of the lens decreases. The focal length of the lens increases.

Question 58.
A child sitting at the back bench 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?
Answer:
Defect is Myopia. This can be overcome by using concave lens of suitable focal length.

Question 59.
A person is not able to see objects beyond 1.3 m. What remedy can you suggest for this defect?
Answer:
Near sightedness. This can be remedied by using concave lens of suitable focal length.

Question 60.
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.
Answer:
Correct statements : a and c

Question 61.
When a person suffering form a problem in vision met a doctor the doctor wrote +2D, -2D in his prescription. Which type of lenses were prescribed here?
Answer:
+2D for convex lens and -2D for concave lens.