Lasers can be used to drill or cut material. One such laser generates a series of high-power pulses of light. Each pulse contains 500 mJ of energy and lasts 10 ns. A lens focuses the light to a 10−μm - diameter circle. What is the light intensity during the pulse?

Question

Lasers can be used to drill or cut material. One such laser generates a series of high-power pulses of light. Each pulse contains 500 mJ of energy and lasts 10 ns. A lens focuses the light to a 10−μm - diameter  circle. What is the light intensity during the pulse?

Philip Williams · Accepted Answer

The peak power of the light pulse is calculated as:  Ppeak=△E△t=500mJ10ns=0.500J1.0×10−8s=5.0×107W  During a pulse, the intensity is calculated as:  Ilaser=Pa=5.0×107Wπ(5.0μm)2=5.0×107W7.85×10−11m2=6.4×1017Wm2

eninsala06 · Accepted Answer

Answer: I=6.4⋅1017Wm2 Explanation: As the intensity of a light source is defined as the light power divided by the illuminated area, we need first to find the power emitted by the laser during the pulse. As power is defined as energy per unit time, we can find the power P as follows: As power is defined as energy per unit time, we can find the power P as follows: P=500e−3J1e−8s=5e7W ⇒P=5⋅107W As the laser is a n⇒ -beam sourse, we can find intensity dividing the power we have just found above, by the area of the circle over which the light is focused: I=PA=5r7Wπ⋅(1e−5m)24=6.4e17Wm2 ⇒I=6.4⋅1017Wm2

Lasers can be used to drill or cut material. One such laser generates

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