(a) Write the expression for the magnification produced by a lens in terms of object distance and image…
(a) Write the expression for the magnification produced by a lens in terms of object distance and image distance.
(b) A 4 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. Calculate the size of the image formed, if the distance of the object from the lens is 10 cm.
Solution
(a)
Image distance
Magnification, m = Object distance / m= u
v
(b) ho= + 4 cm
f = + 20 cm
u = −10 cm
hi =
1
−u= f
v
1
= f +u
v
1
= 20 + −10
v
1 −1
v
= 20
v = −20 cm
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v
m = u
−20
m = −10
m = 2
height of image
m = height of object
height of image = m × height of object
height of image = 2 × 4 cm = 8 cm