Class I Help HW 14 Begin Date: 11/13/2017 11:00:00 AM- Due Date: 11/28/2017 11:0
ID: 1793450 • Letter: C
Question
Class I Help HW 14 Begin Date: 11/13/2017 11:00:00 AM- Due Date: 11/28/2017 11:00:00 AM End Date: 11/28/2017 11:00:00 AM (10%) Problem 10: Laser beams are sometimes used to burn away cancerous tissue. What is the intensity in watts per square meter, of a laser beam that is 90.0% absorbed by a 2.05-mm diameter spot of cancerous tissue and must deposit 520 J of energy to it in a time period of 3.9 s? Grade Summary Deductions 096 Potential 100% sin0 cotan0 cos Attempts remaining: 5 (590 per attempt) detailed view atan acotansinh0 cosh0 tnhcotanh0 Degrees C) Radians Suornitnt I give up! Hints: 1 % deduction per hint. Hints remaining: 1 Feedback: 1% deduction per feedback. Submission History Answer Hints Feedback Totals Totals 0% 096 0% 0%Explanation / Answer
Energy energy absorbed = 520 J
so total energy incident x 90 / 100 = 520
total energy incident = 577.8 J
Power = 577.8 / 3.9 = 148 W
and intensity = Power / Area
= 148 / (pi (2.05 x 10^-3/2)^2)
= 44.9 x 10^6 W/m^2 .........Ans