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When the ciliary muscles are relaxed, th...

When the ciliary muscles are relaxed, the eye lens becomes ......... and its focal length .......... This enables us to see distant objects clearly.

A

thin, increases

B

thin, decreases

C

thick, increases

D

thick, decreases

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The correct Answer is:
A
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When the ciliary muscles contract, the eye lens becomes ......... and its focal length………. This enables us to see nearby objects clearly.

The far point of a myopic eye is 100 cm. What is the focal length of the lens required to see very distant (normal far point) objects clearly?

What change occurs in the focal length, when our eye lens becomes thick ?

Which type of changes occur in thickness or curvature of an eye lens which enables the eye to see the distant and nearby object clearly ?

In the normal situation in the relaxed position of the ciliary muscles, the eye lens is ..........

The ciliary muscles of eye control the curvature of the lens in the eye and hence can alter the effective focal length of the system. When the muscles are fully relaxed, the focal length is maximum. When the muscles are strained, the curvature of lens increases. That means radius of curvature decreases and focal length decreases. For a clear vision, the image must be on the retina. The image distance is therefore fixed for clear vision and it equals the distance of retina from eye lens. It is about 2.5cm for a grown up person. A perosn can theoretically have clear vision of an object situated at any large distance from the eye. The smallest distance at which a person can clearly see is related to minimum possible focal length. The ciliary muscles are most strained in this position. For an average grown up person, minimum distance of the object should be around 25cm. A person suffering from eye defects uses spectacles (eye glass). The function of lens of spectacles is to form the image of the objects within the range in which the person can see clearly. The image o the spectacle lens becomes object for the eye lens and whose image is formed on the retina. The number of spectacle lens used for th eremedy of eye defect is decided by the power fo the lens required and the number of spectacle lens is equal to the numerical value of the power of lens with sign. For example, if power of the lens required is +3D (converging lens of focal length 100//3cm ), then number of lens will be +3 . For all the calculations required, you can use the lens formula and lensmaker's formula. Assume that the eye lens is equiconvex lens. Neglect the distance between the eye lens and the spectacle lens. Q. Maximum focal length of a eye lens of a normal person is

The ciliary muscles of eye control the curvature of the lens in the eye and hence can alter the effective focal length of the system. When the muscles are fully relaxed, the focal length is maximum. When the muscles are strained, the curvature of lens increases. That means radius of curvature decreases and focal length decreases. For a clear vision, the image must be on the retina. The image distance is therefore fixed for clear vision and it equals the distance of retina from eye lens. It is about 2.5cm for a grown up person. A perosn can theoretically have clear vision of an object situated at any large distance from the eye. The smallest distance at which a person can clearly see is related to minimum possible focal length. The ciliary muscles are most strained in this position. For an average grown up person, minimum distance of the object should be around 25cm. A person suffering from eye defects uses spectacles (eye glass). The function of lens of spectacles is to form the image of the objects within the range in which the person can see clearly. The image o the spectacle lens becomes object for the eye lens and whose image is formed on the retina. The number of spectacle lens used for th eremedy of eye defect is decided by the power fo the lens required and the number of spectacle lens is equal to the numerical value of the power of lens with sign. For example, if power of the lens required is +3D (converging lens of focal length 100//3cm ), then number of lens will be +3 . For all the calculations required, you can use the lens formula and lensmaker's formula. Assume that the eye lens is equiconvex lens. Neglect the distance between the eye lens and the spectacle lens. Q. Maximum focal length of a eye lens of a normal person is

The ciliary muscles of eye control the curvature of the lens in the eye and hence can alter the effective focal length of the system. When the muscles are fully relaxed, the focal length is maximum. When the muscles are strained, the curvature of lens increases. That means radius of curvature decreases and focal length decreases. For a clear vision, the image must be on the retina. The image distance is therefore fixed for clear vision and it equals the distance of retina from eye lens. It is about 2.5cm for a grown up person. A perosn can theoretically have clear vision of an object situated at any large distance from the eye. The smallest distance at which a person can clearly see is related to minimum possible focal length. The ciliary muscles are most strained in this position. For an average grown up person, minimum distance of the object should be around 25cm. A person suffering from eye defects uses spectacles (eye glass). The function of lens of spectacles is to form the image of the objects within the range in which the person can see clearly. The image o the spectacle lens becomes object for the eye lens and whose image is formed on the retina. The number of spectacle lens used for th eremedy of eye defect is decided by the power fo the lens required and the number of spectacle lens is equal to the numerical value of the power of lens with sign. For example, if power of the lens required is +3D (converging lens of focal length 100//3cm ), then number of lens will be +3 . For all the calculations required, you can use the lens formula and lensmaker's formula. Assume that the eye lens is equiconvex lens. Neglect the distance between the eye lens and the spectacle lens. Q. Maximum focal length of a eye lens of a normal person is

Which of the following is correct for lens focussing, while seeing distant object ?

KUMAR PRAKASHAN-THE HUMAN EYE AND THE COLOURFUL WORLD-OBJECTIVE QUESTIONS AND ANSWERS (Choose the correct option)
  1. The Sun appears white in afternoon. The reason is ..........

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  2. Sea water at more depth appears blue. The reason is …….....

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  3. When the ciliary muscles are relaxed, the eye lens becomes ......... a...

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  4. When the ciliary muscles contract, the eye lens becomes ......... and ...

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  5. The rainbow on the moon …

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  6. In dispersion of white light due to a triangular glass prism, the devi...

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  7. Which lens from the following, should a person suffering from near-sig...

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  8. Which lens is used by a person suffering from far-sightedness?

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  9. Which of the following is true for near sightedness?

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  10. Which of the following is true for far- sightedness?

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  11. Where is the image formed in the eye of a person suffering from far si...

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  12. A person has a defect of eye vision. His near point is 40 cm. It means...

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  13. A person has a defect of vision. His far point is 1.5 m. It means...

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  14. Out of the following, which light is deviated minimum in the dispersio...

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  15. Which light has maximum speed in glass?

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  16. Which ray of light is present exactly at the middle of the spectrum ob...

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  17. The lens in human eye is a ...........

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  18. For persons suffering from near-sightedness the power of the lens used...

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  19. For a person suffering from .......... the power of the lens used in s...

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  20. Which phenomenon/phenomena of light is / are involved in the formation...

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