Advertisements
Advertisements
प्रश्न
Define the term focal length of a lens.
Advertisements
उत्तर
The distance from the optical centre O of the lens to its second focal point is called the focal length of the lens.
संबंधित प्रश्न
Calculate the focal length of a corrective lens having power +2.5 D.
A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.
The lens mentioned in 6(b) above is of focal length 25cm. Calculate the power of the lens.
The lens A has a focal length of 25 cm whereas another lens B has a focal length of 60 cm. Giving reason state, which lens has more power: A or B.
The power of a lens is, −2 D. What is its focal length?
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?
A symmetric double convex lens is cut in two equal parts by a plane containing the principal axis. If the power of the original lens was 4 D, the power of a divided lens will be
The power of the magnifying glass depends on the distance of the magnifying glass from object.
Power of a lens is – 4D, then its focal length is
An object is kept at a distance of 1m from a lens of power +2D:
- Identify the type of lens.
- Calculate its focal length and distance of the image formed.
