Answer
(a) Not possible
(b) Possible
Work Step by Step
(a) We know that the wavelength of green light is greater than that of blue light and therefore, the frequency of green light is less than that of blue light because $f\propto \frac{1}{\lambda}$. As $E=hf$, hence the energy of a photon of blue light is greater than the energy of a photon of green light. We conclude that the given scenario is not possible.
(b) As the wavelength of green light is less than that of red light, therefore, it is possible (and necessary) for a photon from a green source of light to have more energy than a photon from a red source of light.
