Chapter 17, Problem 44A

To determine

Focus distance of camera.

Answer to Problem 44A

The focus distance of camera is 2.4 m

Explanation of Solution

Given:

The given figure is:

  

The mirror is plane.

A camera distance is 1.2 m in front of mirror so,

  $u=-1.2\text{m}$

Formula Used:

For plane mirror, $v=-u$

Where, $v$ is image distance and $u$ is object distance.

Calculation:

The image distance of a girl is,

  $\begin{array}{c}v=-\left(-1.2\right)\\ =1.2\text{m}\end{array}$

So, the image is 1.2 m inside the mirror.

Now, to take the picture of a girl image in the plane mirror, the camera should focus on the image in the plane mirror.

So, the distance between the camera and girl image in the plane mirror is,

d = camera distance from plane mirror + girl image inside the plane mirror.

  $\begin{array}{c}d=1.2+1.2\\ =2.4\text{m}\end{array}$

Conclusion:

Therefore, the focus distance of camera is 2.4 m