the image of a candle flame formed by a lens is obtained on the screen placed on the other side - Science - Light - Reflection and Refraction

Question

the image of a candle flame formed by a lens is obtained on the
screen placed on the other side of the lens if the image is 3 times
the size of the flame and the distance between lens and image is
80cm, at which distance should the candle be placed from the lens?
what is the nature of the image and find the focal lenght of the
lens??
plzzzzzzzzz replyyy

Hansraj Rai · Accepted Answer

Given that m = 3 v = 80 cm As we know $m = \frac{ν}{u} = \frac{h_{2}}{h_{1}} Using sign convention u is negative and v will be positive as it is formed on the other side of lens 3 = \frac{80}{- u} u = - \frac{80}{3} cm Now, we know \frac{h_{i}}{h_{o}} = \frac{v}{u} = \frac{80}{(- \frac{80}{3})} = - 3 h_{i} = - 3 h_{o} i e as the object height is positive the image height will be negative \Rightarrow i mage is inverted$ $\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \Rightarrow \frac{1}{80} + \frac{3}{80} = \frac{1}{f} \Rightarrow \frac{4}{80} = \frac{1}{f} \Rightarrow f = 20 cm$ As the focal length is positive, the lens will be convex lens