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प्रश्न
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power
विकल्प
+ 0.5 D
– 0.5 D
+ 0.2 D
– 0.2 D
उत्तर
– 0.5 D
Explanation -
The person is suffering from myopia. He needs a concave lens and hence power would be negative.
Object distance, u = - ∞
Image distance, υ = -2 m
Using lens formula
`1/upsilon - 1/"u" = 1/"f"`
`1/f = 1/(-2) - 1/∞`
f = -2 m
`P = 1/f = -1/(2 "m") = -0.5 "D"`
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संबंधित प्रश्न
What is the:
near point of a normal human eye?
Define the term "power of accommodation" of human eye.
Describe the working of the human eye with the help of the above diagram.
Explain the functions of the following parts of the eye:
(i) cornea
(ii) iris
(iii) pupil
(iv) ciliary muscles
(v) eye-lens
fill in the following blank with suitable word:
A person is short-sighted if his eyeball is too............Spectacles with a .............lens are needed. A person is long-sighted if his eyeball is too............Spectacles with a ................lens are needed. These focus light rays exactly on to the..........
Name the muscles of the eye responsible for the power of accommodation.
What are the functions of tears?
Choose the Odd One Out:
| Column I | Column II | ||
| 1 | Retina | a | Path way of light |
| 2 | Pupil | b | Far point comes closer |
| 3 | Ciliary muscles | c | near point moves away |
| 4 | Myopia | d | Screen of the eye |
| 5 | Hypermetropia | e | Power of accomodation |
Give reason:
Blind spot is considered as 'area of no vision'.
