danago
Nov10-06, 10:27 PM
"A concave mirror of focal length 1m is used to magnify an object by a factor of 4. Where is the object in relation to the pole of the mirror?"
Heres what i did:
\begin{array}{c}
M = \frac{v}{u} \\
\therefore 4 = \frac{v}{u} \\
\therefore v = 4u \\
\end{array}
\begin{array}{c}
\frac{1}{f} = \frac{1}{u} + \frac{1}{v} \\
\therefore 1 = \frac{1}{u} + \frac{1}{{4u}} = \frac{5}{{4u}} \\
\therefore u = 1.25m \\
\end{array}
Where am i going wrong? According to my textbook, the answer is 0.75m.
Thanks in advance,
Dan.
Heres what i did:
\begin{array}{c}
M = \frac{v}{u} \\
\therefore 4 = \frac{v}{u} \\
\therefore v = 4u \\
\end{array}
\begin{array}{c}
\frac{1}{f} = \frac{1}{u} + \frac{1}{v} \\
\therefore 1 = \frac{1}{u} + \frac{1}{{4u}} = \frac{5}{{4u}} \\
\therefore u = 1.25m \\
\end{array}
Where am i going wrong? According to my textbook, the answer is 0.75m.
Thanks in advance,
Dan.