The human retina has three types of receptor cones, each sensitive to a different range of wavelengths of visible light, as shown in this figure (the colors are merely to differentiate the three curves from one another; they do not indicate the actual colors represented by each curve):

(a) Estimate the energies of photons with wavelengths at the maximum for each type of cone.
(b) The color of the sky is due to scattering of solar light by the molecules of the atmosphere. Lord Rayleigh was one of the first to study scattering of this kind. He showed that the amount of scattering for very small particles such as molecules is inversely proportional to the fourth power of the wavelength. Estimate the ratio of the scattering efficiency of light at the wavelength of the maximum for the "blue" cones, as compared with that for the "green" cones.
(c) Explain why the sky appears blue even though all wavelengths of solar light are scattered by the atmosphere.

Transcribed Image Text:

400 500 600 700 Wavelength (nm