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Question
How will you differentiate between a convex and a concave lens by looking at a printed page?
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Solution
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.
RELATED QUESTIONS
What is a lens?
Study the diagram shown in the following Figure.
Name the lens LL’ and draw its outline.
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.
What type of lenses are used in spectacles worn by an old lady for knitting?
In the following diagram the object and the image formed by the respective lenses are shown. Complete the ray diagram, and locate the focus. Find the focal length of the lens.
In the following diagram , the object and the image formed by the respective lenses are shown. Complete the ray diagram, and locate the focus. Find the focal length of the lens.
Fig. shows two rays of light Op and OQ coming from an object at the bottom of a pond, incident on the water surface.
(a) Mark on the diagram
(i) The angle of incidence of ray OP,
(ii) The angle of refraction of ray Op,
(iii) The position of image of the object as seen from above.
(iv) An approximate path of the ray OQ.
(b) Explain, why do the rays of light change directions on passing from water to air.
(c) A fish in water sees everything outside the water by rays of light entering its eye in a small cone of light. Draw a diagram and explain how does this happen.
When does a ray of light falling on a lens pass through it undeviated?
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.
Complete the following diagram and state what happens to the ray of light after refraction through the lens.
