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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
Kavita from 10th is using spectacles. The power of the lenses in her spectacles is –2.5 dioptre. Answer the following questions:
1) Which lenses are used in her spectacles?
2) State the defect of vision Kavita is suffering from.
3) Find the focal length of the lenses used in her spectacles
State the condition for the following a ray passes undeviated through the lens .
How does the power of a lens change if its focal length is doubled?
On reducing the focal length of a lens, its power ______.
How does focal length of a lens change when red light incident on it is replaced by violet light? Give reason for your answer.
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 lens forms an upright and diminished image of an object, irrespective of its position. What kind of lens is this? Draw an outline ray diagram to show the formation of the image. State the position and one more characteristic of the image.
If there is a convex lens of focal length 75 cm and a concave lens of focal length 40 cm, then calculate their combined power and combined focal length.
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.
A point object is placed at O in front of a glass sphere as shown in figure.
Show the formation of the image by the sphere.
