Cls 10 Sci Chp 11 prvs aprd quns

       Class 10 Science

Previous Years  Appeared Questions and Answers    

  Chapter 11 Human Eye and Colorful World     

           Multiple Choice Questions     

1. The sky as seen from the surface of the moon appears dark because, (Sep - 2020)

(A) only a little of the blue and violet colours are scattered

(B) all the colours are absorbed by the atmosphere present in the moon

(C) all the colours are scattered Total

(D) atmospheric particles needed to scatter the light are not present.

Ans. : (D) atmospheric particles needed to scatter the light are not present.

2. Right statement regarding the colour of the scattered sunlight and the size of scattering atmospheric particles is (April 2024) 

(A) small particles scatter red colour 

(B) big particles scatter blue colour 

(C) big particles scatter violet colour 

(D) too larger particles scatter all colours equally 

Ans. : (D) too larger particles scatter all colours equally 

3. The colour that is least scattered by fog and smoke is (June 2024) 

(A) orange    (B) blue   (C) red    (D) violet 

Ans. : (C) red 

4. Identify the wrong statement among the following statements regarding refraction and dispersion of light. (June 2024) 

(A) Stars twinkle 

(B) Sky appears blue to an astronaut flying at very high altitudes 

(C) The sun is visible to us about two minutes before the actual sunrise 

(D) Planets do not twinkle 

Ans. : (B) Sky appears blue to an astronaut flying at very high altitudes

5. The crystalline lens of the eye in old age people sometimes becomes milky and cloudy. This condition is called (kseeb mqp 2 2025)

(A) Hypermetropia       (B) Myopia            

(C) Presbyopia                (D) Cataract

Ans: (D) Cataract

  One Mark Questions              

1. A student sitting in the last bench has difficulty in reading the blackboard writing. Which is the defect of vision the student has ? How can it be corrected ? (Sep - 2020)

Ans. :

★ The student is suffering from Myopia.

★ This defect is corrected by using a concave lens of suitable power.

2. What is the function of pupil of the human eye ? (June -2019)

Ans:

It controls the amount of light that enters the eye.

3. What is spectrum of white light ? (Aug 2024) 

Ans. : The band of the coloured components of a white light beam is called spectrum of white light.

4. Observe the below figure showing the refraction of light through a glass prism. (June 2024) 

 

      

Ans: .

 ★ X → Angle of deviation 

★ The peculiar shape of the prism makes the emergent ray bend at an angle to the direction of the incident ray

Two Marks Questions            

1. Draw the diagram showing the hypermetropic eye. (June - 2020)

Ans. : 

2. (i) What is Tyndall effect?

(ii) Name the colour that bends the least and the colour that bends the most when white light is dispersed by a prism. (June 2019)

Ans:

(i) The phenomenon of scattering of a beam of light by colloidal particles, when passed through a colloidal solution, is called the Tyndall effect”.

(ii) The light that bends the least is red colour and the light that bends the maximum is violet colour light.

                          

3. (i) What is meant by the power of accommodation of the eye ?

(ii) What are the far point and near point of the human eye with normal vision ? (June 2019)

Ans: 

(i) Power of accommodation is the ability of the eye lens to focus near and far objects clearly on the retina by adjusting its focal length.

(ii) For a young adult with a normal vision, the near point is about 25 cm and the far point of the eye is at infinity. A normal eye can see objects clearly that are between 25 cm and infinity.

4. What is hypermetropia or far-sightedness ? Name the type of lens used to correct it. (June 2019)

Ans:

Hypermetropia or far-sightedness is a defect of the eye in which nearby objects appear blurry but distant objects are clear. It can be corrected using a convex lens of suitable focal length.

5. Draw the diagram to represent the recombination of the spectrum of white light. Label the following parts : (i) Prism (ii) Screen. (June 2019)

Ans:

6. What is spectrum of white light ? Name any two phenomenon that occur in the atmosphere due to the refraction of light. (April 2024)

Ans. : The band of coloured components of a light beam formed by the splitting of light through glass prism is called spectrum of light. 

 Phenomena that occur due to the refraction of light : 

★ Twinkling of stars 

★ Advanced sunrise and delayed sunset 

★ Rainbow formation. 

7. What is cataract of eye ? What is the near point and far point of the human eye with normal vision ? (April 2024)

Ans. : 

The crystalline lens of people at old age becomes milky and cloudy. This condition is called cataract. 

★ The near point : 25 cm 

★ The far point : Infinity. 

8. A person who has a defect of the eye as shown in the below figure purchases a spectacle having lens of – 2·0D power. Is this lens suitable to rectify the eye defect of that person ? Analyse. (April 2024)

Ans. : 

★ This lens is not suitable for that person’s defect of eye. 

★ Light rays from a closeby object are focussed at a point behind the retina. 

★ Therefore it is farsightedness and it is corrected by using a convex lens of appropriate power in spectacle. 

★ Lens of – 2·0 D power is a concave lens and that does not rectify this defect. 

9. Draw the ray diagrams that show : 

i) Near point of hypermetropic eye 

ii) Hypermetropic eye 

iii) Correction for hypermetropic eye. (April 2024)

Ans:

 

              Three Marks Questions            

1. a) Draw the diagram to show the recombination of the spectrum of white light and label the following parts.

b) The ray of light that bends the most The ray of light that bends the least. (Sep - 2020)

Ans:

Total Recombination of spectrum of white light :

2. a) How does the eye accommodate to see far and near objects ? 

b) Why do stars twinkle ? Explain. (Aug 2024) 

Ans. : 

 a) The eye lens is composed of a fibrous, jelly like material. Its curvature can be modified to some extent by the ciliary muscles. The change in curvature of the eye lens can thus change its focal length. When the muscles are relaxed, the lens becomes thin, thus focal length increases. This enables us to see distant objects clearly. 

When you are looking at objects closer to the eyes, the ciliary muscles contract. This increases the curvature of the eyes lens. The eye lens becomes thicker. Consequently, the focal length of the eye lens decreases. This enables us to see nearby objects clearly. 

 b) The twinkling of star is due to atmospheric refraction of sunlight. 

The starlight, on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index.  

Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. This apparent position is not stationary, but keeps on changing slightly. 

Since the stars are very distant, they approximate point sized sources of light. As the path of rays of light coming from the stars goes on varying slightly, the apparent position of the stars fluctuates and the amount of starlight entering the eye flickers — the star sometimes appears brighter, and at some other time, fainter, which is the twinkling effect. 

Five Marks Questions              

1. Explain the experiment conducted by Newton to show that white light contains seven colours. Sun appears red in colour during sunrise but appears white at noon. Explain with the reasons. (June - 2020)

Ans. :

★ Isaac Newton was the first to use a glass prism to obtain the spectrum of sun light.

★ He tried to split the colours of the spectrum of white light further by using similar prism. He could not get any more colours.

★ He then placed a second prism (identical) in an inverted position with respect to the first prism. This allowed all the colours of the spectrum to pass through the second prism.

★ He found a beam of white light emerging from the other side of the second prism. This observation gave Newton the idea that the sun light is made up of seven colours.

★ Light from the sun near the horizon passes through thicker layers of air and larger distance in the earths atmosphere before reaching our eyes.

★ Near the horizon most of the blue light and shorter wavelengths are scattered away by the particles.

★ Therefore the light that reaches our eyes is of longer wavelength. This gives the reddish appearance to the sun.

★ However light from the sun overhead would travel relatively shorter distance.

★ At noon, the sun appears white as only a little of the blue and violet colours are scattered.