the image of candle flame placed at a distance of 40cm from a spherical lens is formed on a sccreen placed on the other side of the lens at a distance of 40cm from the lens . identify the types of lens and write its focal length . what will be the nature of the image formed if the candle flame is shifted 25cm towards the lens ? draw ray diagram to justify.

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Solution

Since the image can be formed on a screen, the image is a real image. Only a convex lens can form a real image, so the lens is a convex lens.
Given
u = -40cm
v = 40 cm
Find f.
here u = v
Now, we know that when the object is at 2F, the image is formed at 2F.
Hence, u = v = 2F = 40 cm
this means that F = 20 cm
Now, when the object is shifted 25 cm towards the lens, u = (-40+25) = -15 cm
The object is now between F and O. As you must have read, the image formed will be virtual.

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The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?

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