An object 5 cm tall is placed perpendicular to the principal axis of a convex lens of focal length 15 cm.…
An object 5 cm tall is placed perpendicular to the principal axis of a convex lens of focal length 15 cm. The distance of the object from the lens is 30 cm. Find: (a) the position of the image, (b) the size (height) of the image, (c) the nature of the image formed.
Solution
Given $f = +15 \, \text{cm}$, $u = -30 \, \text{cm}$, $h = 5 \, \text{cm}$.
(a) $\frac{1}{v}$ - $\frac{1}{u}$ = $\frac{1}{f}$ => $\frac{1}{v}$ = $\frac{1}{15}$ + $\frac{1}{-30}$ = $\frac{1}{30}$ => $v = +30 \, \text{cm}$ (image 30 cm on the other side of the lens).
(b) $m = \frac{v}{u}= \frac{30}{-30} = -1 \Rightarrow h' = m \times h = -5 \, \text{cm}$, so the image is 5 cm tall and inverted.
(c) The image is real, inverted and the same size as the object.
Asked in: CBSE Class 10 Physics — Light (Reflection & Refraction) SET A