Advertisements
Advertisements
Question
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.
Advertisements
Solution
Power varies inversely with the focal length. Lens A has a small focal length and hence, more power.
APPEARS IN
RELATED QUESTIONS
What is meant by a power of a lens? Define its SI unit.
How unit of power related to focal length of a lens?
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
Ranbir claims to have obtained an image twice the size of the object with a concave lens. Is he correct? Give a reason for your answer.
What can you see in a completely dark room? If you switch on an electric bulb in this dark room as a light source, explain how you could now see:
(a) the electric bulb
(b) a piece of white paper
Give the usual name for the following:
A point inside a lens through which the light passes undeviated.
Which type of lens has (a) a positive power, and (b) a negative power?
Which of the two has a greater power: a lens of short focal length or a lens of large focal length?
A lens has a focal length of, −10 cm. What is the power of the lens and what is its nature?
A combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.A optical instrument in which the above arrangement of convex lens is used is a convex lens used to burn paper by focusing sunlight.
State the condition for the following a lens has both its focal lengths equal .
How does the power of a lens change if its focal length is doubled?
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
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.
If focal length of a convex lens is 20 cm at what is the power of the lens?
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.
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.
