Question

A concave mirror gives an image 5 times as large an object focal length of the concave mirror is 10cm. For the image to be virtual. Find the image distance

• A. +40cm
• B. -40cm
• C. +60cm
• D. -60cm

Answer 1

The correct option is A +40cm

$\begin{array}{c}{h}_1=5h_0\\ f=-10\end{array}$

For the image to be virtual magnification should be positive

$\begin{array}{cc}-\frac{V}{u}=& +ve\\ & \text{so}\frac{hz}{h_0}=5\\ & \text{magnification}=5\\ -\frac{y}{u}& =5\\ v& =-5u\end{array}$

formula

$\frac{1}{f}=\frac{1}{V}+\frac{1}{u}$

$\begin{array}{c}\frac{1}{-10}=\frac{1}{-5\mu }+\frac{1}{4}\\ -\frac{1}{10}=\frac{-1+5}{5\mu }\\ u=-8\mathrm{con}\\ v=(-5)(-8)=+40cm\end{array}$

Option $A$ is correct