Q.The focal length of concave mirror is 20 cm. At what distance should a 4 cm long object be placed from this mirror so that its image is formed at a distance of 30 cm. Also, calculate size of the image formed.
Q.When an object is kept at a distance of 12 cm from lens, the real image formed by it is 2/3 times the size of object. Calculate the focal length of lens.
Q .The power of a lens is +5 D. What is the nature and focal length of lens. At what distance
from this lens, the object be placed so that an inverted image of same size is obtained.
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Answer: A1: u = 60cm in front of mirror, size of image=8cm
Explanation: Sorry I was only able to tell you answer of first
use formulas: 1/f = 1/u + 1/v
magnification = I/O= v/u
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