Can someone pleaae explain this calculation to me. I am so LOST. and I do not un

Question

Can someone pleaae explain this calculation to me. I am so LOST. and I do not understand why it is wrong when I solved like this: Power = 2.0mJ/(16ns)=0.125 what is: 2*10^-3 / (16*10^-9) ? The problem is below this line.

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LASIK eye surgery uses pulses of laser light to shave off tissue from the cornea, reshaping it. A typical LASIK laser emits a 1.0-mm-diameter laser beam with a wavelength of 193 nm. Each laser pulse lasts 16ns and contains 2.0mJ of light energy. What is the power of one laser pulse? During the very brief time of the pulse, what is the intensity of the light wave?

Now, Power of a pulse is the energy it carries/ the lifetime of a pulse Power = 2.0mJ/(16ns) = 2*10^-3 / (16*10^-9) = 1.25 * 10 ^5 W = 125 kW Intensity = Power / area of the pulse area of pulse = Pi * r^2 = Pi* (1mm/2)^2 = Pi * (10^-3/2)^2 = 7.85 * 10^-7 m^2 Intensity = 125 * 10^3 / (7.85 * 10^-7) = 15.92 * 10^10 W/m^2

Explanation / Answer

d =1 mm, R = 0.5 mm, Q = 2 mJ, t =16 ns

Power =Q/t = (2x10-3)/(16x10-9)

P = 1.25x105 W

I= P/As =P/(4pi*R2)

I = (1.25x105)/[4x3.14x (0.5x10-3)2]

I = 3.98x109 W/m2

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