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Question
State whether concave lens has a real focus or a virtual focus.
Solution
A concave lens has a virtual focus because the light rays do not actually pass through the focus.
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RELATED QUESTIONS
If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished, what is the nature of this lens? Draw a ray diagram to justify your answer.
A small bulb is placed at the focal point of a converging lens. When the bulb is switched on, the lens produces:
(a) a convergent beam of light
(b) a divergent beam of light
(c) a parallel beam of light
(d) a patch of coloured light
A converging lens of focal length 5 cm is placed at a distance of 20 cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?
If the image formed by a lens is always diminished and erect, what is the nature of the lens?
- Name the lens which always forms an erect and virtual image.
- State whether the image in part (a) is magnified or diminished.
A concave lens forms a magnified or diminished image depending on the distance of an object from it.
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Draw a ray diagram to justify your answer for the above situation and label it.
Draw neat diagram to show the
Divergent action of concave lens
State three characteristics of the image of an extended source, formed by a concave lens.
