# Problem: a) What is the intensity in W/m² of a laser beam used to burn away cancerous tissue that, when 89.5% absorbed, puts 497 J of energy into a circular spot 2.01 mm in diameter in 4.00 s? b) How many times more intense is this than the maximum intensity of direct sunlight (about 1360 W/m²)?

###### FREE Expert Solution

Intensity of the beam:

$\overline{)\begin{array}{rcl}{\mathbf{I}}& {\mathbf{=}}& \frac{\mathbf{E}}{\mathbf{A}\mathbf{t}}\\ & {\mathbf{=}}& \frac{\mathbf{E}}{\mathbf{\pi }{\mathbf{r}}^{\mathbf{2}}\mathbf{t}}\end{array}}$

a)

r = 2.01/2 = 1.005 mm

###### Problem Details

a) What is the intensity in W/m² of a laser beam used to burn away cancerous tissue that, when 89.5% absorbed, puts 497 J of energy into a circular spot 2.01 mm in diameter in 4.00 s?

b) How many times more intense is this than the maximum intensity of direct sunlight (about 1360 W/m²)?