Question

What is the intensity in W/m2 of a laser beam used to burn away cancerous tissue that, when 85.0% absorbed, puts 470 J of energy into a circular spot 2.60 mm in diameter in 4.00 s?

Answer 1

26036485.6433 W/m²

Step-by-step explanation:

E= Energy = 470 J

t = Time = 4 seconds

d = Diameter = 2.6 mm

Power is given by

`P=(E)/(t)`

Intensity is given by

`I=(P)/(\pi r^2)\\\Rightarrow 0.85I=(E)/(t(\pi)/(4) d^2)\\\Rightarrow I=(470)/(0.85* 4* (\pi)/(4)* (2.6* 10^(-3))^2)\\\Rightarrow I=26036485.6433\ W/m^2`

The intensity of the laser beam is 26036485.6433 W/m²