Problems are listed in approximate order of difficulty. A single dot (•) indicates straightforward problems involving just one main concept and sometimes requiring no more than substitution of numbers in the appropriate formula. Two dots (••) identify problems that are slightly more challenging and usually involve more than one concept. Three dots (•••) indicate problems that are distinctly more challenging, either because they are intrinsically difficult or involve lengthy calculations. Needless to say, these distinctions are hard to draw and are only approximate.
• A lightbulb that is rated at 60 W actually produces only about 3 W of visible light, most of the rest of the energy being infrared (or heat), (a) About how many visible photons does such a lightbulb produce each second? Use the average value λ ≈ 550 nm. (b) If a person looks at such a bulb from about 10 ft away, about how many visible photons enter the eye per second? (When looking at a bright light, the pupil has a diameter of about 1 mm.) (c) By how many powers of 10 does this exceed the minimum detectable intensity, which is about 100 photons entering the eye per second?
We need at least 10 more requests to produce the solution.
0 / 10 have requested this problem solution
The more requests, the faster the answer.