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प्रश्न
How will you differentiate between a convex and a concave lens by looking at a printed page?
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उत्तर
On keeping the lens near a printed page, if the letters appear magnified, then the lens is convex, and if the letters appear diminished, then the lens is concave.
संबंधित प्रश्न
Explain optical centre of a lens with the help of proper diagram(s).
Study the diagram shown in the following Figure.
Name the lens LL’ and draw its outline.

Study the diagram shown in Fig. 5.56
Where is the image formed?

The diagram given below shows the position of an object OA in relation to a converging lens whose foci are at F1 and F2.

Describe how the distance of the image from the lens and the size of the image change as the object is moved towards F1.
State the condition of the following:
A lens has both its focal lengths equal.
Define the term focus of a lens.
A lens forms the image of an object placed at a distance of 45 cm from it on a screen placed at a distance 90 cm on the other side of it. Name the kind of lens.
The diagram showed a lens as a combination of one glass block and two prisms. Complete the ray diagram and show the part of the incident ray AB after passing through the lens.
(i) Name of the lens formed by the combination.
(ii) What is the line XX’ called?
(iii) Mark the focus F.

