Advertisements
Advertisements
Question
Surabhi from std. X uses spectacle. The power of the lenses in her spectacle is 0.5 D.
Answer the following questions from the given information:
- Identify the type of lenses used in her spectacle.
- Identify the defect of vision Surabhi is suffering from.
- Find the focal length of the lenses used in her spectacle.
Advertisements
Solution
1) The power is positive hence the convex lens
2) Hypermetropia
3) `"P" =1/"F"`
`"f" = 1/"P" = 1/0.5 = 2 "m"`
= 200 cm
APPEARS IN
RELATED QUESTIONS
Calculate the focal length of a corrective lens having power +2.5 D.
Find the power of a concave lens of focal length 2m.
What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses.
(a) At what distance should the lens be held from the figure in order to view the squares distinctly with the maximum possible magnifying power?
(b) What is the magnification in this case?
(c) Is the magnification equal to the magnifying power in this case? Explain.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
Which one of the following materials cannot be used to make a lens?
How is the power of a lens related to its focal length?
What is the power of a convex lens of focal length 0.5 m?
The power of a lens is + 0.2 D. Calculate its focal length.
A lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5D. Find (i) the focal length of the lens, and (ii) the size of the image.
A diverging lens has a focal length of 0.10 m. The power of this lens will be:
Define the term focal length of a lens.
How is the power of a lens related to its focal length?
How is the sign (+ or -) of power of a lens related to its divergent or convergent action?
A thin converging lens is formed with one surface convex and the other plane. Does the position of image depend on whether the convex surface or the plane surface faces the object?
A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and its is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens
A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is double of the other. Find the radii, if the refractive index of the material of the lens is 1.5.
A convex lens produces a double size real image when an object is placed at a distance of 18 cm from it. Where should the object be placed to produce a triple size real image?
A diverging lens of focal length 20 cm and a converging lens of focal length 30 cm are placed 15 cm apart with their principal axes coinciding. Where should an object be placed on the principal axis so that its image is formed at infinity?
How is accommodation produced?
A lens forms an upright and diminished image of an object, irrespective of its position. What kind of lens is this? Draw an outline ray diagram to show the formation of the image. State the position and one more characteristic of the image.
If the lens is of focal length 25 cm. Calculate the power of the lens.
If focal length of a convex lens is 20 cm at what is the power of the lens?
Increase in the converging power of eye lens cause ‘hypermetropia'
Match the following:
| 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 accommodation |
Assertion and reasoning type
- Assertion: Myopia is due to the increase in the converging power of eye lens.
- Reason: Myopia can be corrected with the help of concave lens.
A convex lens with radii of curvature R1 = R2 is immersed in water. Assuming that the refractive indices of glass and water are 3/2 and 4/3 respectively, its focal length f1 in comparison to that in air, f, is ______.
An object is placed in front of a converging lens. Obtain the conditions under which the magnification produced by the lens is
- negative and
- positive.
A point object is placed at O in front of a glass sphere as shown in figure.
Show the formation of the image by the sphere.
When monochromatic red light is used instead of blue light in a convex lens, its focal length will ______.
The focal length of a double convex lens is equal to the radius of curvature of either surface. What is the refractive index of its material?
The lens of power + 1·0 D is ______.
