Ray Optics Question 9
Question 9 - 2024 (30 Jan Shift 2)
In an experiment to measure the focal length (f) of a convex lens, the magnitude of object distance (x) and the image distance (y) are measured with reference to the focal point of the lens. The $y-x$ plot is shown in figure.
The focal length of the lens is $cm$.
Show Answer
Answer: (20)
Solution:
$\frac{1}{f+20}-\frac{1}{-(f+20)}=\frac{1}{f}$
$\frac{2}{f+20}=\frac{1}{f} \quad f=20 cm$
Or $x _1 x _2=f^{2}$ gives $f=20 cm$
