Advertisements
Advertisements
प्रश्न
Solve the following question:
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
उत्तर
Since the near point of the eye is 50 cm which is greater than 25 cm, a person is suffering from hypermetropia.
Object distance (u) = - 25cm
Image distance (v) = - 50cm
Using lens formula
`1/"f" = 1/"v" - 1/"u"`
`1/"f" = 1/(-50) - 1/(-25)`
`1/"f" = -1/50 + 1/25`
`1/"f" = (-1+2)/50`
`1/"f" = 1/50`
`"f"` = +50 cm
Since the focal length of the lens is positive, corrective lens required is convex lens.
`"f"` = +50cm
`"f"` = +0.5m
Power (P) of corrective lens will be
`"P" = 1/("f"("m"))`
`"P" = 1/0.5`
`"P" = + 2 "D"`
APPEARS IN
संबंधित प्रश्न
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
Name the body part with which the terms myopia and hypermetropia are connected.
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What are the two conditions shown in sections A and B of the eye as applicable to her?
Anuja cannot see the blackboard writing but she can see nearby things.
(a) What is the eye defect she is suffering from?
(b) State the possible reason for her defect.
(c) How is it corrected
Study the following diagram carefully and then answer the questions that follow. The diagram is depicting a defect of the human eye :
(i) Identify the defect shown in the diagram.
(ii) Give two possible reasons for the above defect.
With respect to human eye explain:
(i) How is the image formed on the retina?
(ii) How is the amount of light entering the eye-controlled?
(iii) What type of lens is used for the correction of ‘Long sight’ defect?
(iv) With the help of a ray, diagram show the defect of the eye and then its correction after the use of a lens.
Which of the following statement is correct?
