Option 1 states that Albert Einstein received the Nobel Prize in Physics for explaining the photoelectric effect. This statement is correct. Einstein was awarded the Nobel Prize in 1921 for his discovery of the law of the photoelectric effect.

Option 2 states that for each metal, there is a threshold frequency below which the photoelectric effect is not observed. This statement is also correct. The threshold frequency, also known as the cutoff frequency, is the minimum frequency of light required to eject an electron from a metal surface. If the frequency of the incident light is below the threshold frequency, no electrons will be ejected.

Option 3 states that at a frequency greater than vQ (the threshold frequency), the kinetic energy of ejected electrons does not change with an increase in the frequency of incident light. This statement is incorrect. According to the photoelectric effect equation, the kinetic energy of ejected electrons is directly proportional to the frequency of the incident light. Therefore, as the frequency of the incident light increases, so does the kinetic energy of the ejected electrons.

Option 4 states that the number of electrons ejected is proportional to the intensity of the incident light. This statement is also correct. The intensity of light refers to the number of photons per unit area per unit time. The photoelectric