Jeremiah Ruesch, a contributor for Edutopia, writes: "When do you know it's time to try something different in your math lesson? For me, I knew the moment I read this word problem to my fifth-grade summer school students: 'On average, the sun's energy density reaching Earth's upper atmosphere is 1,350 watts per square meter. Assume the incident, monochromatic light has a wavelength of 800 nanometers (each photon has an energy of 2.48 × 10-19 joules at this wavelength). How many photons are incident on the Earth's upper atmosphere in one second?'" more

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