Laser Safety A 095 mW laser emits a narrow beam of light tha

Laser Safety A 0.95 mW laser emits a narrow beam of light that enters the eye, as shown in the figure (Figure 1) How much energy is absorbed by the eye in 0.20 s? Express your answer using one significant figure. E = 0.2 mJ The eye focuses this beam to a tiny spot on the retina, perhaps 5.0 mum in diameter. What is the average intensity of light at this spot? Express your answer using two significant figures. Laser Safety A 0.95 m W laser emits a narrow beam of light that enters the eye, as shown in the figure (Figure 1) The eye focuses this beam to a tiny spot on the retina, perhaps 5.0 mum in diameter. What is the average intensity of light at this spot? Express your answer using two significant figures. Damage to the retina can occur if the average intensity of light exceeds 1.0 Times 10^2 W/cm^2. By what factor has the intensity of this laser beam exceeded the safe value? Express your answer using two significant figures.

Solution

Energy = (P)(t) = (0.95X 10^-3)(0.2) = 0.19 X 10^-3 J = 0.2 mJ

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Intensity = Power/Area = P / r²

                                     = [0.95X 10^-3] /()(2.5 X 10^-6)²

                                    = 4.838X 10⁷ W/m²

                                    = 4.838X 10³ W/cm²

                                    = 4.838 X 10³ kW/cm²

Part C)

f = 4.838 X 10³/1 X 10^-2 = 4.838 X 10⁵