Question

Question 35
The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?

Answer 1

Given, the magnification m= 3
Image distance, v = 80 cm
Object distance = u
Using formula,
$m=-\frac{v}{u}$
$\Rightarrow u=-\frac{v}{m}$
$=-\left(\frac{80}{3}\right)$
$=-26.67cm$
Thus, the object must be placed 26.67 cm from the lens.
If the image is formed at a distance of 80 cm, it is real and inverted and the lens is a convex lens.