When the wavelength of incident light in photoelectric effect decreases, then photoelectron's

Question

Accepted Answer

In the photoelectric effect, when the wavelength of the incident light decreases, the energy of the photons increases. This is because the energy of a photon is inversely proportional to its wavelength, as described by the equation $E = \frac{hc}{\lambda}$, where $E$ is the energy, $h$ is Planck's constant, $c$ is the speed of light, and $\lambda$ is the wavelength. Therefore, a decrease in wavelength results in an increase in photon energy.

1. **Explanation for Option 4 (Correct Answer):**  
   When the energy of the incident photons increases (due to a decrease in wavelength), the maximum kinetic energy of the emitted photoelectrons also increases. This is because the energy of the incident photon is transferred to the photoelectron, and after overcoming the work function (the minimum energy required to eject an electron from the surface), the remaining energy is converted into the kinetic energy of the photoelectron. Thus, a higher photon energy results in a higher maximum kinetic energy for the photoelectrons.

2. **Explanation for why other options are incorrect:**

- **Option 1 (Number increases):**  
     The number of photoelectrons emitted depends on the intensity of the incident light, not directly on the wavelength. A decrease in wavelength increases the energy of individual photons but does not necessarily increase the number of photons or photoelectrons unless the intensity (number of photons per unit area per unit time) is also increased.

- **Option 2 (Maximum kinetic energy decreases):**  
     This option is incorrect because, as explained, a decrease in wavelength results in an increase in photon energy, which leads to an increase, not a decrease, in the maximum kinetic energy of the photoelectrons.

- **Option 3 (Number decreases):**  
     Similar to Option 1, the number of photoelectrons is not directly affected by the wavelength but by the intensity of the light. A decrease in wavelength alone does not imply a decrease in the number of photoelectrons unless the intensity is altered.

In conclusion, Option 4 is correct because a decrease in the wavelength of the incident light increases the energy of the photons, thereby increasing the maximum kinetic energy of the emitted photoelectrons.