BIO High-Energy Cancer Treatment. Scientists are working on a new technique to k
ID: 1460641 • Letter: B
Question
BIO High-Energy Cancer Treatment. Scientists are working on a new technique to kill cancer cells by zapping hem with ultra-high energy (in the range of 1012 W) pulses of light that last for an extremely short time ( a few nanoseconds). These short pulses scramble the interior of a cell without causing it to explode, as long pulses would do. We can model a typical such cell as a disk 5.0m in diameter, with the pulse lasting for 4.0ns with an average power of 2.0 × 1012 W. We shall assume that the energy is spread uniformly over the faces of 100 cells for each pulse. (a) How much energy is given to the cell during this pulse? (b) What is the intensity (in W/m2) delivered to the cell? (c) What are the maximum values of the electric and magnetic fields in the pulse?
Explanation / Answer
a) energy given to the cell during this pulse = power*time
= 2*10^12*4*10^-9
= 8000 J
b) Area od one cell = pi*d^2/4
= pi*(5*10^-6)^2/4
= 1.96*10^-11 m^2
Area of 100 cells, A = 1.96*10^-9 m^2
now Intensity, I = power/Area
= 2*10^12/(1.96*10^-9)
= 1.02*10^21 W/m^2
c) Intensity of light wave, I = Emax^2/(2*c*mue)
Emax = sqrt(2*I*c*mue)
= sqrt(2*1.02*10^21*3*10^8*4*pi*10^-7)
= 8.77*10^11 N/c
Bmax = Emax/c
= 8.77*10^11/(3*10^8)
= 2923 T
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