A regular LED light bulb continuously emits 10.0 W of light uniformly in all directions. A man stands so that his eyes are 5.00 m away from this light bulb and he is looking directly at the light bulb. There are no other sources of light in this room. (a) What is the irradiance of this light in W/m2 just before entering this man's eyes? (b) If each pupil of this man is contracted to a radius of 2.00 mm, what is the total power in W of the light entering each eye? (c) A human receives 3300 J of usable energy after eating one blueberry. How long would this man have to stare at this light bulb in order to take into his eyes through the pupils the same amount of energy as eating a blueberry? Don't forget that he has two eyes! (Note that far more energy from the light is hitting his skin, but that is not what we care about here.)

A regular LED light bulb continuously emits 10.0 W of light uniformly in all directions. A man stands so that his eyes are 5.00 m away from this light bulb and he is looking directly at the light bulb. There are no other sources of light in this room. (a) What is the irradiance of this light in W/m2 just before entering this man's eyes? (b) If each pupil of this man is contracted to a radius of 2.00 mm, what is the total power in W of the light entering each eye? (c) A human receives 3300 J of usable energy after eating one blueberry. How long would this man have to stare at this light bulb in order to take into his eyes through the pupils the same amount of energy as eating a blueberry? Don't forget that he has two eyes! (Note that far more energy from the light is hitting his skin, but that is not what we care about here.)

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter24: Electromagnetic Waves

Section: Chapter Questions

Problem 53P

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