Question

The intensity of radiation at a distance x meters from a source is modeled by the function given by R(x)=kx2, where kk is a positive constant. Which of the following gives the average intensity of radiation between 10 meters and 50 meters from the source?

Answer 1

This would be the average value of R(x) between 10 m and 50 m :

$\displaystyle \frac1{50\,\mathrm m - 10\,\mathrm m} \int_{10\,\rm m}^{50\,\rm m} kx^2 \, dx$