Chapter 11 - Human eye and colourful world Extra Questions

1.  What does eye accommodation ability mean?

Explanation:

 from both close and far objects on the retina with clarity.


2. The eye's accommodation power, or capacity to change its focal length, allows it to concentrate ligh .

A myopic individual cannot clearly see objects that are farther away than 1.2 meters. What sort of corrective lens should be worn to restore clear vision?

Explanation:

To correct myopia, a person with the affected eye should use a curved lens with a focal length of 1.2 m.


3. What are the near and far acuities of the human eye when viewing normally?

Explanation:

The nearest distance at which an object can be plainly seen without strain is the near point of the eye. For a normal person's eye, this distance measures 25 centimeters.

  • The eye's far point is the furthest place from which an object can be clearly seen. The far end of an average individual is infinite.


4. The very last student in the row has difficulty seeing the blackboard. What condition(s) or flaw(s) could the baby have? How can it be corrected?

Explanation:

Myopia, or short-sightedness, affects the iris. It is possible to treat myopia with concave glasses.


5. The focal length of the eye lens allows the human eye to concentrate on objects at various distances. This is because

(A) Presbyopia

(B)Arrangements

(C)  Nearsightedness 

(D) having long eyes

Explanation:

(B)  Arrangements

Reason :

The human eye can concentrate on objects at various distances by changing the focal length of the eye lens thanks to accommodation.


6. An object's picture is formed by the human eye at its

  1. cornea 

  2. eye

  3. Student

  4. The retina

Explanation:

© The retina

Reason : 

The layer of nerve cells that lines the rear wall of the eye is called the retina. This layer detects light and communicates with the brain to enable vision.


7. For a youthful adult with normal vision, the shortest distance of distinct vision is approximately

  1. 25 m

  2. 2.5 cm

  3.  25 cm

  4. 2.5 m

Explanation:

  ©  25 cm

Reason : 

The shortest distance at which a young adult with normal eyesight can see clearly is 25 cm.


8. The action of the causes the shift in focal length of an eye lens.

  1. Student

  2. The retina

  3. ciliary muscles 

  4. Eye

Explanation:

 © Ciliary muscles

Reason :

The focus length of an eye lens is altered by the ciliary muscles.


9. A -5.5 dioptre lens is required to fix someone’s distance vision. He requires a +1.5 dioptre lens to fix his near vision. What lens focal length is necessary to rectify (i) farsightedness and (ii) nearsightedness?

Explanation:

A lens’s power (P) is determined by the relationship for a particular focal length (f).

Power (P) equals 1/f

  1. The lens’s power (used to adjust distance vision) is -5.5 D

  The lens’s focal length (f) equals 1/P

F = 1/-5.5

F = -0.181 m

The lens’s focal length (to compensate for distance vision) is -0.181 m.

( ii ) The lens’s power (used to correct near eyesight) is +1.5 D.

The necessary lens’s focal length (f) is equal to 1/P.

F = 1/1.5 = +0.667 m


10. A myopic person’s far spot is 80 cm in front of the eye. What type and strength of glass is needed to solve the issue?

Explanation:

Myopia is a problem for the person. The image is created in front of the retina in this defect. In order to rectify this visual flaw, a concave lens is used.

The object's distance (u) Is infinite, so

80 centimetres is the image distance (v)

F = focal range

The algorithm for the lens states that


11. Why is it that objects closer than 25 cm distant are blurry to the average eye?

Explanation:

Normal eyes are unable to distinguish things closer than 25 cm because their ciliary muscles can only contract so far.


12. As the distance between an item and the eye increases, what happens to the image distance in the eye?

Explanation:

The image of an object is still created on the retina even when it is farther from the eye. The distance between the object and the eye causes the eye lens to become smaller and its focal length to lengthen.


13. How come stars twinkle?

Explanation:

The refraction of sunlight by the atmosphere is what causes a star to twinkle. Before reaching the earth, the starlight is constantly refracted as it travels through the atmosphere. A medium with a steadily changing refractive index is where the atmospheric refraction takes place.


14.  Describe the reason the planets don't sparkle

Explanation: 

Planets are not like stars that shine. Even when viewed through a telescope, stars are so far away that they only show as pinpoints of light in the night sky. The path of the light is extremely vulnerable to atmospheric interference because all of the light originates from a single spot. (i.e. their light is easily diffracted).


15.  Why does the Sun look ruddy in the early morning hours?

Explanation: 

Before it reaches the observer, white light emitted by the sun must traverse a greater distance through the atmosphere. Only the red-colored light gets the observer as a result of the scattering of all other colored lights during this process but the red light. As a result, at sunrise and sunset, the sun looks reddish.


16. Why does an astronaut see the heavens as black rather than blue?

Explanation: 

Astronauts see the sky as being black rather than blue because there is no light scattering outside of the earth's atmosphere.