Advertisements
Advertisements
प्रश्न
The focal length of a lens is negative. In this case, state the kind of lens.
उत्तर
The negative focal length of a lens indicates that it is a concave lens.
APPEARS IN
संबंधित प्रश्न
Where must the object be placed for the image formed by a converging lens to be:
real, inverted and same size as the object?
State whether concave lens has a real focus or a virtual focus.
If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed 19 cm from the lens, the image formed is slightly larger than object. The approximate focal length of the lens is ______.
An object 2 cm tall stands on the principal axis of a converging lens of focal length 8 cm. Find the position, nature and size of the image formed if the object is:
(i) 12 cm from the lens
(ii) 6 cm from the lens
State one practical application each of the use of such a lens with the object in position (i) and (ii).
With the help of a diagram, explain why the image of an object viewed through a concave lens appears smaller and closer than the object.
State one practical use each of convex mirror, concave mirror, convex lens and concave lens.
Which of the following can form a virtual image which is always smaller than the object?
(a) a plane mirror
(b) a convex lens
(c) a concave lens
(d) a concave mirror
When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object.
What is the focal length of lens A?
Complete the following sentence:
A short-sighted person cannot see ............ objects clearly. Short-sightedness can be corrected by using ........... lenses.
A person cannot see distant objects clearly. His vision can be corrected by using the spectacles containing:
(a) concave lenses
(b) plane lenses
(c) contact lenses
(d) convex lenses
