Chapter 16, Problem 41A

To determine

To Write:A problem of the given solution.

Explanation of Solution

Introduction:

The given solution is $95$

  $\text{lx}$ $=\frac{1100}{4\pi r^2}$

Here $95$ lx is the illumination of source denoted by $\text{E}$ , and 1100 lm is the luminous flux denoted by $\text{P}$ and r is the distance of the source from the paper.

The expression for illumination is

  $\text{E=}\frac{\text{P}}{{\text{4πr}}^{\text{2}}}$   ...... (1)

Here, $\text{E}$ is the illumination, $\text{P}$ is the luminous flux and r is the distance of the source from the paper.

The question can be:

To find the distance of the bulb source above a sheet of paper if an illumination of is 95 lx and having luminous flux 1100 lm.