The image of a candle flame place at a distance of 36 cm from a spherical lens is formed on a screen place at a distance of 72 cm from the lens. Identify the type of lense and calculate its focal length. If the height of the flame is 2.5 cm, find the height of the image.
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Answer:
A) Convex lens
B) + 24 cm
C) - 5 cm
Explanation:
Given: Object distance, u=-36
Image distance, V=+72
The image is Real and is depicted with the help of positive sign.
height of the object, h1 = 2.5 cm
Applying the lens formula, we get
1/f = 1/v - 1/u
1/f = 1/72 - 1/-36
1/f = 3/72
f = +24 cm
Since the focal length is positive, so the lens will be a convex lens of focal length 24 cm.
M = v/u
= 72 / -36
= -2
M is also = Height of the image / height of object
-2 = h of image / 2.5
Height of the image = -5 cm
The negative sign depicts that the image is inverted. The nature of the image formed will be:
1. Real
2. Inverted
3. Magnified
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