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प्रश्न
Define the term focal length of a lens.
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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 +2D.
Consider two statements A and B given below:
A: real image is always inverted
B: virtual image is always erect
Out of these two statements:
An object of height 4 cm is placed at a distance of 15 cm in front of a concave lens of power, −10 dioptres. Find the size of the image.
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?
A double convex lens has two surfaces of equal radii R and refractive index \[m = 1 \cdot 5\]
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?
Focal length : metre : : power of lens : _______
The above lens has a focal length of 10 cm. The object of height 2 mm is placed at a distance of 5 cm from the pole. Find the height of the image.
The lens of power + 1·0 D is ______.
