MCQ
The graph shows how the magnification $m$ produced by a convex thin lens varies with image distance $v$. What was the focal length of the used
- A$\frac{b}{c}$
- B$\frac{b}{{ca}}$
- C$\frac{{bc}}{a}$
- ✓$\frac{c}{b}$
Comparing it with $y = mx + c$
Slope $ = m = - \frac{1}{f}$
From graph, slope of the line $ = \frac{b}{c}$
Hence $ - \frac{1}{f} = \frac{b}{c}$ ==> $|\,f|\, = \frac{c}{b}$
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