An object is placed at a distance of 100 cm from a converging lens of focal length 40 cm.
(i) What is the nature of image?
(ii) What is the position of image?
A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.
(i) Since the object is placed at a distance greater than the focal length of the lens, so the image formed is real and inverted.
(ii) u = -100 cm, f = 40 cm
Lens formula: \(\frac{1}{v}\) - \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{v}\) - \(\frac{1}{-100}\) = \(\frac{1}{40}\)
\(\frac{1}{v}\) = \(\frac{1}{40}\) = \(\frac{1}{100}\)
\(\frac{1}{v}\) - \(\frac{5 - 2}{200}\) = \(\frac{3}{200}\)
v = 66.6 cm
Image is formed 66.6 cm behind the convex lens.