Human Eye and the Colorful World ||10th Science || Intext & Exercise Question || CBSE

Human Eye and the Colorful World || CBSE

Dear Students, Today we are going to share the Intext Question of Human Eye and Colorful World. These question are very helpful for the students of Class 10 as per the latest syllabus of CBSE/State Board. We are regularly update such types of useful post for the students

Human eye is one of the most valuable sense organ

Notes      Intext Question     Exercise Question

Intext Question

Question 1:_ What is meant by power of accommodation of the eye?

Answer:_ The ability of eye lens to adjust its focal length to view both distant and nearby objects on the retina is called the power of accommodation of the eyes.

Question 2:_ A person with a myopic eye cannot see object beyond 1.2 m distinctly. What should be the types of the corrective lens used to restore proper vision?

Answer:_ The person is able to see nearby objects clearly but he is unable to see objects beyond 1.2 m.

To correct this defect of vision he must use a concave lens.

Question 3:_ What is the far point and near point of human eye with normal vision?

Answers:_ The near point of the eye is the minimum distance of the object from the eye, which can be seen distinctly without strain. For normal eye this distance is 25 cm.

The far point of the eye is the maximum distance to which the eye can see the objects clearly. The far point of the normal human eye is infinity.

Question 4:_ A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?

Answer:_ If a student has difficulty in reading the blackboard while sitting in the last row. It shows that he is unable to see distant object clearly. He is suffering from myopia. This defect can be corrected by using concave lens.

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Exercise

Question 1:_ The human eye can focus object at different distance by the focal length of the eyes. This is due to

(a) Presbyopia

(b) Accommodation

(c) Near-sightedness

(d) Far-sightedness

Answer:_ (b) This is due to the power of accommodation of eyes.

Question 2:_ The human eye form the image of an object at its

(a) Cornea

(b) Iris

(c) Pupil

(d) Retina

Answer:_ (d) Retina.

 Question 3:_ The least distance of distinct vision for a young adult with normal vision is about

(a) 25 m

(b) 2.5 m

(c) 25 cm

(d) 2.5 cm

Answer: (d) 25 cm

Question 4:_ The change in focal length of an Eyes lens is caused by the action of the:-

(a) Pupil

(b) Retina

(c) Cilliary muscles

(d) Iris

Answer:_ Cilliary muscles.

Question 5:_ A person needs a lens of power ─ 5.5 dioptre for correcting his vision distant vision. For correcting his near vision he need a lens of power + 1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision (ii) near vision?

Answer:_ (i) We know that the power of the lens of the focal length f is a given by

The focal length of a lens for correcting vision is ─ 0•181 m.

(ii) Power of lens = + 1•5 D

The focal length of the lens for correcting vision is 0•667m

Question 6:_ The far point of a myopic person is 80 cm in front of the eyes. What is the nature and power of the lens required to correct the problem?

Answer:_ The person is suffering from an eye defect called myopia. In this defect the image is formed in front of the retina. Hence a concave lens is used to correct this defect of vision.

 Object distance u = ∞

Image distance v = ─ 80 cm

Focal length = f

According to Lens formula

\ A concave lens of power ─ 1.25 D is required.

Question 7:_ Make a diagram to show how hyper-metropia is corrected. The near point of hypermetropia eye is 1 m. What is the power of lens required to correct the defect. Assume that the near point of the normal eyes is 25 cm.

Answer:_ The defect of vision is collected by using a convex lens. A convex lens of suitable focal length converge the incoming light in such a way that the image is formed on the retina as shown in figure

Here: Object distance u =

Image distance v =

Let focal length = f

Using the lens formula

 

A convex lens of power + 3.0 D is required to correct the defect.

Question 9:_ What happens to the image distance in the eye when we increase the distance of an object from the eyes?

Answer:_ Since the size of eyes cannot change i.e. cannot increase or decrease, the image distance remains constant. When we increase the distance of an object from the eye. The image distance in the eye does not change. The increase in the object distance is a compensated by the change in the focal length of the eye lens. The focal length of the eye lens is a change in such a way that the image is formed at the retina of the eyes.

Question 10:_ Why do star Twinkle?

Answer:_ Star emits their own light and they twinkle due to atmospheric refraction of light. Stars are very far away from the earth and they are considered.

Question 11:_ Why planets do not twinkle?

Answer:_ Planet do not twinkle because they appear larger in size then the star as they are relatively close to earth. Planet can be considered as a collection of large number of point sizes source of light. The different part of these planets produces either brighter or dimmer effect in such a way that the average of brighter and dimmer effect is zero. Hence the twinkling effects of the planets are nullified and they do not twinkle.

Question 12:_ Why does the sun appear reddish early in the morning?

Answer:_ During sunrise, the light comings from the sun have to travel a greater distance in the earth’s atmosphere before reaching our eyes. In this journey, the shorter wavelength of light are scattered out and only longer wavelength able to reach our eyes. Since blue colour has a shorter wavelength and red colour have a longer wavelength. The red colour is able to reach our eyes after the atmospheric scattering of light. Therefore, the sun appears reddish early in the morning.

Question 13:_ Why does the sky appear dark instead of blue to the astronaut?

Answer:_ The sky appears dark instead of blue to an astronaut   because they are there is no atmosphere in the outer space that can scatter the sunlight. As the sunlight is not scattered. No scattered light reach the eyes of astronaut and the sky appear black to them.