Light of wavelength 180nm strikes a metal target and photoelectrons are emitted. It is noticed that the photocurrent drops to zero at stopping potential of 0.8 V. The work function of the metal surface is___________a.None of theseb.5.03 eVc.6.09 eVd.3 eVe.3.7 eV
Question
Light of wavelength 180nm strikes a metal target and photoelectrons are emitted. It is noticed that the photocurrent drops to zero at stopping potential of 0.8 V. The work function of the metal surface is___________a.None of theseb.5.03 eVc.6.09 eVd.3 eVe.3.7 eV
Solution 1
To solve this problem, we need to use the photoelectric effect equation:
E = hf - Φ
where E is the energy of the emitted photoelectron, h is Planck's constant, f is the frequency of the incident light, and Φ is the work function of the metal.
First, we need to convert the wavelength of the light to frequency using the equation:
f = c/λ
where c is the speed of light (3 x 10^8 m/s) and λ is the wavelength. The wavelength needs to be in meters, so we convert 180 nm to 180 x 10^-9 m.
f = (3 x 10^8 m/s) / (180 x 10^-9 m) = 1.67 x 10^15 Hz
Next, we can calculate the energy of the photoelectron using the stopping potential. The energy is given by:
E = eV
where e is the charge of an electron (1.6 x 10^-19 C) and V is the stopping potential (0.8 V).
E = (1.6 x 10^-19 C)(0.8 V) = 1.28 x 10^-19 J
Now we can solve for the work function Φ:
Φ = hf - E
Substituting the values we have:
Φ = (6.63 x 10^-34 J.s)(1.67 x 10^15 Hz) - 1.28 x 10^-19 J = 1.28 x 10^-19 J
Converting this to electron volts (eV) by dividing by the charge of an electron:
Φ = 1.28 x 10^-19 J / 1.6 x 10^-19 C = 0.8 eV
So, the work function of the metal surface is not listed in the options provided. The correct answer is "None of these".
Solution 2
To solve this problem, we need to use the photoelectric effect equation:
E = hf - Φ
where E is the energy of the emitted photoelectron, h is Planck's constant, f is the frequency of the incident light, and Φ is the work function of the metal.
First, we need to convert the wavelength of the light to frequency using the equation:
f = c/λ
where c is the speed of light (3 x 10^8 m/s) and λ is the wavelength. The wavelength needs to be in meters, so we convert 180 nm to 180 x 10^-9 m.
f = (3 x 10^8 m/s) / (180 x 10^-9 m) = 1.67 x 10^15 Hz
Next, we calculate the energy of the photoelectron using the stopping potential. The energy is given by:
E = eV
where e is the charge of an electron (1.6 x 10^-19 C) and V is the stopping potential.
E = (1.6 x 10^-19 C)(0.8 V) = 1.28 x 10^-19 J
Now we can solve for the work function Φ:
Φ = hf - E
Substituting the values we have:
Φ = (6.63 x 10^-34 J.s)(1.67 x 10^15 Hz) - 1.28 x 10^-19 J = 9.28 x 10^-19 J
To convert this to electron volts (eV), we divide by the charge of an electron:
Φ = (9.28 x 10^-19 J) / (1.6 x 10^-19 C) = 5.8 eV
So, the work function of the metal surface is not listed in the options provided. The correct answer should be "None of these".
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