Statement of a problem № 10396


A 0.75-mW laser emits a narrow beam of light that enters the eye, as shown in FIGURE 25-41. In Figure 25-41 (a) How much energy is absorbed by the eye in 0.2 s? (b) The eye focuses this beam to a tiny spot on the retina, perhaps 5.0 mm in diameter. What is the average intensity of light (in W/cm2) at this spot? (c) Damage to the retina can occur if the average intensity of light exceeds 1.0 × 10-2 W/cm2. By what factor has the intensity of this laser beam exceeded the safe value?

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