Question:
An object is placed beyond the centre of curvature $\mathrm{C}$ of the given concave mirror. If the distance of the object is $\mathrm{d}_{1}$ from $\mathrm{C}$ and the distance of the image formed is $d_{2}$ from $C$, the radius of curvature of this mirror is :
Correct Option: 1
Solution:
Using Newton"s formula
$\left(f+d_{1}\right)\left(f-d_{2}\right)=f^{2}$
$\mathrm{f}^{2}+\mathrm{fd}_{1}-\mathrm{fd}_{2}-\mathrm{d}_{1} \mathrm{~d}_{2}=\mathrm{f}^{2}$
$\mathrm{f}=\frac{\mathrm{d}_{1} \mathrm{~d}_{2}}{\mathrm{~d}_{1}-\mathrm{d}_{2}}$
$\therefore \mathrm{R}=\frac{2 \mathrm{~d}_{1} \mathrm{~d}_{2}}{\mathrm{~d}_{1}-\mathrm{d}_{2}}$