An object 2 cm tall is placed on the axis of a convex lens of focal length 5 cm at a distance of 10 m from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?
\(h_1\) = 2 cm
f= 5 cm
u = -10 m = -1000 cm
\(\frac{1}{v}\) - \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{v}\) - \(\frac{1}{-1000}\) = \(\frac{1}{5}\)
\(\frac{1}{v}\) = \(\frac{1}{5}\) - \(\frac{1}{1000}\)
= \(\frac{200 - 1}{1000}\) = \(\frac{199}{1000}\)
v = 5.02 cm
The image is formed 5.02 cm behind the convex lens and is real and inverted.
m = \(\frac{v}{u}\) = \(\frac{5.02}{-1000}\)
= -0.005
m = \(\frac{h_2}{h_1}\) = -0.005
\(\frac{h_2}{2}\) = -0.005
\(h_2\) = -0.01 cm
Since the object distance is much greater than the focal length, this example illustrates the case when the object is place.