an object when placed infront of a convex lens forms a real image of 0.5 magnification.If the distance of the image from the lens is 14cm,calculate the focal length of the lens
Answers
Answer:
It is given that image distance [v] = 24 cm.
The magnification [m] = 0.5
As per the rule of sign convention for lens, the measurement taken opposite to the direction of light is taken as negative.
As the image is real, so the image must be formed on the other side of the lens .
Hence, v = +24 cm
As the image is real, so the magnification is taken as negative.
Hence, m = -0.5
We are asked to calculate the focal length [f] of the lens.
The magnification in terms of v and f is given as -
m=\frac{f-v}{f}
⇒ mf=f-v
⇒ f\ = \frac{v}{1-m}
=\frac{(24)}{1-(-0.5)}
=16\ cm
Hence, the focal length of the convex lens is 16 cm.
Explanation: