Question

A concave lens has a focal length of -31 {cm}. Find the image distance and magnification that results when an object is placed 29 {cm} in front of the lens.
d1= ? cm
m= ?

Answer 1

Answer:

The value is $v = 440 \ cm$

and  

 $m = 16$

Explanation:

From the question we  are told that

    The image  distance is  $v = 29 \ cm$

    The focal length is $f = -31 \ cm$

From the lens equation we have that

      $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$

=>    $\frac{1}{-31} = \frac{1}{v} - \frac{1}{29}$

=>     $v = 450 \ cm$

Generally the magnification  is  

      $m = \frac{v}{u}$

=>    $m = \frac{ 450}{29}$

=>    $m = 16$