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प्रश्न
Explain the following term related to spherical lenses: focal length
उत्तर
Focal Length:-
The focal length of a lens is the distance between optical centre and principal focus of the lens.
संबंधित प्रश्न
Define the following term in the context of spherical mirrors:- Principal focus
Name the mirror which always produces an erect and virtual image. How is the size of image related to the size of object?
When an object of height 1 cm is kept at a distance 4 cm from a concave mirror, its erect image of height 1.5 cm is formed at a distance 6 cm behind the mirror. Find the focal length of mirror, by drawing.
Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed :
(i) between the optical centre and principal focus of a convex lens.
(ii) anywhere in front of a concave lens.
(iii) at 2F of a convex lens.
State the signs and values of magnifications in the above-mentioned cases (i) and (ii).
An object forms a virtual image which is 1/8th of the size of the object. If the object is placed at a distance of 40 cm from the convex mirror, calculate:
- the position of the image
- the focal length of the convex mirror.
Define the following term:
concave mirror
Define the following term in relation to concave mirror.
Radius of curvature
Assertion: Incident ray is directed towards the centre of curvature of spherical mirror. After reflection it retraces its path.
Reason: Angle of incidence (i) = Angle of reflection (r) = 0°
