Advertisements
Advertisements
प्रश्न
Which type of lens has (a) a positive power, and (b) a negative power?
Advertisements
उत्तर
(a) Convex lens has positive power.
(b) Concave lens has negative power.
APPEARS IN
संबंधित प्रश्न
You have two lenses A and B of focal lengths +10 cm and –10 cm, respectively. State the nature and power of each lens. Which of the two lenses will form a virtual and magnified image of an object placed 8 cm from the lens? Draw a ray diagram to justify your answer
Kavita from 10th is using spectacles. The power of the lenses in her spectacles is –2.5 dioptre. Answer the following questions:
1) Which lenses are used in her spectacles?
2) State the defect of vision Kavita is suffering from.
3) Find the focal length of the lenses used in her spectacles
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
The focal length of a convex lens is 25 cm. What is its power?
A diverging lens has focal length of 3 cm. Calculate the power.
The power of a lens is, −2 D. What is its focal length?
A convex lens of power 5 D and a concave lens of power 7.5 D are placed in contact with each other. What is the :
(a) power of this combination of lenses?
(b) focal length of this combination of lenses?
Two lenses A and B have focal lengths of +20 cm and, −10 cm, respectively.
(a) What is the nature of lens A and lens B?
(b) What is the power of lens A and lens B?
(c) What is the power of combination if lenses A and B are held close together?
How does the power of a lens change if its focal length is doubled?
On reducing the focal length of a lens, its power ______.
Express the power (with sign) of a concave lens of focal length 20 cm.
A symmetric double convex lens in cut in two equal parts by a plane perpendicular to the principal axis. If the power of the original lens was 4 D, the power a cut-lens will be
Consider the situation described in the previous problem. Where should a point source be placed on the principal axis so that the two images form at the same place?
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.
A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above.
Focal length : metre : : power of lens : _______
The power of the magnifying glass depends on the distance of the magnifying glass from object.
Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm. What is the nature of the lens and its power used by each of them?
