A student performed the experiment of determination of focal length of a concave mirror by $u-v$ method…
A student performed the experiment of determination of focal length of a concave mirror by $u-v$ method using an optical bench of length $1.5 \mathrm{~m}$. The focal length of the mirror used is 24 $\mathrm{cm}$. The maximum error in the location of the image can be $0.2 \mathrm{~cm}$.
The 5 sets of $(u, v)$ values recorded by the student (in $\mathrm{cm})$ are : $(42,56),(48$, $48),(60,40),(66,33),(78,39)$. The data set(s) that cannot come from experiment and is (are) incorrectly recorded, is(are)
$(42,56)$
$(48,48)$
$(66,33)$
$(78,39)$
Solution
Values of options (c) and (d) don't match with the mirror formula,
$
\frac{1}{v}+\frac{1}{u}=\frac{1}{f}
$