The graph shows how the reciprocal of magnification (∣∣∣μ=43∣∣∣) produced by a converging thin lens varied with object distance u in displacement method. What was the focal length of the lens used?
By applying lens formula 1v−1u=1f
1v=f+uuf; m=vu ⇒ ff+u; 1m=uf+1
Slope of 1m and ′u′ is 1f ∴ 1f=bc ⇒ f=cb