Radiation of wavelength 2500 am strong is incident on the metal plate ...
Key Points:
- Incident radiation has a wavelength of 2500 am.
- The work function of the metal plate is 3.5 eV.
- We need to calculate the potential required to stop the fastest emitted electrons.
Explanation:
1. Understanding the Work Function:
The work function of a metal is the minimum amount of energy required to remove an electron from its surface. When radiation of sufficient energy is incident on a metal surface, electrons can be emitted through the photoelectric effect.
2. Relation between Energy and Wavelength:
The energy of a photon is related to its wavelength by the equation: E = hc/λ, where E is the energy, h is the Planck's constant (6.626 x 10^-34 J·s), c is the speed of light (3 x 10^8 m/s), and λ is the wavelength.
3. Calculating the Energy of Incident Radiation:
Since the wavelength of the incident radiation is given as 2500 am (attometer), we need to convert it to meters. 1 am = 10^-18 m.
Wavelength in meters (λ) = 2500 am x 10^-18 m/am = 2.5 x 10^-15 m
Using the energy-wavelength relation, we can calculate the energy (E) of the incident radiation:
E = hc/λ = (6.626 x 10^-34 J·s) x (3 x 10^8 m/s) / (2.5 x 10^-15 m) = 7.9512 x 10^-19 J
4. Determining the Maximum Kinetic Energy of Electrons:
The maximum kinetic energy (KEmax) of emitted electrons is given by the difference between the energy of the incident radiation and the work function of the metal:
KEmax = E - work function
The work function is given as 3.5 eV. To convert eV to Joules, we use the conversion factor: 1 eV = 1.6 x 10^-19 J.
Work function in Joules = 3.5 eV x (1.6 x 10^-19 J/eV) = 5.6 x 10^-19 J
KEmax = 7.9512 x 10^-19 J - 5.6 x 10^-19 J = 2.3512 x 10^-19 J
5. Finding the Required Potential:
The potential required to stop the fastest emitted electrons is equal to their maximum kinetic energy. Using the equation:
KEmax = eV
where e is the elementary charge (1.6 x 10^-19 C) and V is the potential, we can solve for V:
V = KEmax / e = (2.3512 x 10^-19 J) / (1.6 x 10^-19 C) = 1.4695 V
Thus, the potential required to stop the fastest emitted electrons is approximately 1.47 V.
Radiation of wavelength 2500 am strong is incident on the metal plate ...
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