Final answer:
The student's query relates to the photoelectric effect in physics, where light causes electrons to be ejected from a metal's surface, provided the photon energy exceeds the binding energy of the electrons. The different observations reported pertain to the kinetic energy of photoelectrons ejected by light of varying wavelengths.
Step-by-step explanation:
The student's question involves the photoelectric effect, a phenomenon observed in physics. When light of different wavelengths strikes a metallic surface, electrons can be ejected if the energy of the photons exceeds the binding energy that holds the electrons to the metal. The energy (E) of a photon is given by E = hf, where h is Planck's constant and f is the frequency of the light. The frequency can be found using c = λf, where λ is the wavelength of the light and c is the speed of light. The kinetic energy (KE) of the ejected electrons is then found by subtracting the binding energy (BE) of the metal from the energy of the incident photons (E = hf - BE).
Observation a corresponds to no photoelectrons being observed, which implies that the energy of the photons with a wavelength of 336 nm was not sufficient to overcome the binding energy of the electrons to the metal surface.
Observation b, which shows photoelectrons with a kinetic energy of 160 kJ/mol, indicates that the photons with a wavelength of 438 nm had enough energy not only to overcome the binding energy but also to impart additional kinetic energy to the ejected electrons.
Observation c refers to photoelectrons with a lower kinetic energy of 49 kJ/mol, ejected by light with a wavelength of 644 nm. This suggests that the energy of these photons was also above the binding energy, but by a smaller margin compared to the photons of 438 nm.