Question 81: Ray Optics

Question

If the distance between object and its two times magnified virtual image produced by a curved mirror is $$15 \mathrm{~cm}$$, the focal length of the mirror must be:

Accepted Answer

$$\begin{aligned}
& \mathrm{m}=2=\frac{-v}{u} \
& 2=\frac{-(15-u)}{-u} \
& 2 u=15-u \
& 3 u=15 \Rightarrow u=5 \mathrm{~cm} \
& v=15-u=15-5=10 \mathrm{~cm} \
& \frac{1}{f}=\frac{1}{v}+\frac{1}{u} \
& =\frac{1}{10}+\frac{1}{(-5)}=\frac{1-2}{10}=\frac{-1}{10} \
& f=-10 \mathrm{~cm}
\end{aligned}$$

Answer

$$-10$$ cm

Answer

$$-12$$ cm

Answer

15 cm

Answer

10/3 cm

Ray Optics

If the distance between object and its two times magnified virtual image produced by a curved mirror is $15 \mathrm{~cm}$, the focal length of the mirror must be:

Choose the correct answer: