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प्रश्न
If the numerical value of the power of this lens is 10 D, what is its focal length in the Cartesian system ?
उत्तर
Since, power of a lens is given by the relation
`P=1/f` (in metres)
p = 10 D (given)
`10 = 1/f`
`f = 1/10`
`f= 0.1 m`
Therefore, the focal length of the lens is 0.1 m as the lens is concave in nature.
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संबंधित प्रश्न
Explain with the help of a diagram, why the concave lens is also called a diverging lens.
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).
What type of image is always made by a concave lens?
An object is placed on the axis of a lens. An image is formed by refraction in the lens. For all positions of the object on the axis of the lens, the positions of the image are always always between the lens and the object Draw a ray diagram to show it.
At what distance from a concave lens of focal length 20 cm a 6 cm tall object be placed so as to obtain its image at 15 cm from the lens? Also calculate the size of the image formed.
Draw a ray diagram to justify your answer for the above situation and label it.
A virtual diminished image is formed when an object is placed between the optical centre and the principal focus of a lens.
(i) Name the type of lens which forms the above image.
(ii) Draw a ray diagram to show the formation of the image with the above stated characteristics.
Distinguish between:
Concave Lens and Convex Lens
The focal length of a lens is negative. In this case, state the kind of lens.
