Question

NOTE: All of the parts of this question deal with visible light. You will need to choose a typical wavelength for light in the visible spectrum before making any of these calculations. Please enter your choice in the box below and submit your answer before proceeding. (An incorrect answer here will not cost you any points.)

? = _______ nm

(a) The human eye can detect a flash of light consisting of as few as ten photons if they fall in a sufficiently small area on the fovea, a particularly sensitive region of the retina. How much energy is in such a flash?

______ J

(b) Plants photosynthesize glucose from carbon dioxide and water: 6 CO₂ + 6 H₂O ? C₆H₁₂O₆ + 6 O₂. It requires 2.88 x 10⁶ joules of energy (which plants obtain from visible light) to synthesize one mole of glucose this way. Approximately how many photons are required for a plant to synthesize a single glucose molecule?

______ photons

(c) The intensity of sunlight striking the Earths surface is approximately one kilowatt per square meter. Estimate how many photons per second would strike a square solar panel 2.00 m on a side. Assume that the panel is facing directly towards the Sun.

_______ photons

Answer 1