In photoelectric effect, work function of martial is \(3.5 \mathrm{eV}\). By applying \(-1.2 \mathrm{~V}\) potential, photo electric current becomes zero, so......... (A) energy of incident photon is \(4.7 \mathrm{eV}\). (B) energy of incident photon is \(2.3 \mathrm{eV}\) (C) If photon having higher frequency is used, photo electric current is produced. (D) When energy of photon is \(2.3 \mathrm{eV}\), photo electric current becomes maximum

To calculate the energy of the emitted electron, we can use the equation for the photoelectric effect: \(E = W + KE\) where \(E\) is the energy of the incident photon, \(W\) is the work function of the material (given as 3.5 eV), and \(KE\) is the kinetic energy of the emitted electron. When photoelectric current becomes zero, this means that the kinetic energy of the emitted electron is also zero. Thus, the equation becomes: \(E = W\) Since the work function is already given, we can plug in the value: \(E = 3.5 \ \mathrm{eV}\)

The stopping potential is -1.2 V, which means that the kinetic energy of the maximum energetic electrons is converted into potential energy to overcome this voltage. Using the formula \(KE = e \times V\), where \(e\) is the elementary charge and \(V\) is the potential. We can calculate the additional energy provided by the stopping potential: \(\Delta KE = e \times (-1.2) = -1.2 \ \mathrm{eV}\)

To find the energy of the incident photon, we need to add the stopping potential influence to the original electron energy calculated in the first step: \(E = 3.5 \ \mathrm{eV} -1.2 \ \mathrm{eV} = 2.3 \ \mathrm{eV}\) So, the energy of the incident photon is 2.3 eV. Now, we can evaluate the given statements: (A) energy of incident photon is \(4.7 \ \mathrm{eV}\) - This is incorrect. (B) energy of incident photon is \(2.3 \ \mathrm{eV}\) – This is correct. (C) If a photon having a higher frequency is used, a photoelectric current is produced. - This is correct. A higher frequency photon will have more energy, and thus could have enough energy to eject electrons from the material and produce photoelectric current. (D) When the energy of a photon is \(2.3 \ \mathrm{eV}\), the photoelectric current becomes maximum - This is incorrect. The maximum photoelectric current is influenced by the intensity of the incident light, and will not necessarily be achieved with a photon of \(2.3 \ \mathrm{eV}\). In conclusion, the correct statements are (B) and (C).