Question

5 cm tall object is placed 10 cm in front of an unknown mirror. A virtual image is formed 3.5 cm behind the mirror (a) Calculate the focal length of the mirror (b) What type of mirror is this (concave or convex)? (c) Calculate the height of the image (d) Determine whether the image is inverted or upright?

Answer 1

$h_o= 5cm$

$d_o= 10cm$

$a)$

$d_i = -3.5cm$

$\frac{1}{f}=\frac{1}{d_0}+\frac{1}{d_i}$

$f= \frac{d_0d_i}{d_0+d_i}= \frac{-3.5*10}{10-3.5}=-5.38$

$\text{Answer: }5.38cm$

$b)$

$f<0 \text{ then this is a convex mirror}$

$\text{Answer: convex mirror}$

$c)$

$M = -\frac{-d_i}{d_0}=0.35$

$h_i = Mh_0= 0.35*5 = 1.65$

$\text{Answer: }1.65cm$

$d)$

$M>0 ;$ \text{image is upright}

$\text{Answer: image is upright}$