The stopping potential of the photoelectrons, from a photo cell is
- directly proportional to intensity of incident light
- directly proportional to frequency of incident light
- inversely proportional to frequency of incident light
- Inversely proportional to intensity of incident light
The Correct Option is B
Solution and Explanation
More the kinetic energy of emitted electrons, higher is the potential needed to stop them (stopping potential).
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Top MHT CET Photoelectric Effect Questions
In a photoelectric effect experiment, light of wavelength \( \lambda \), \( \lambda/2 \), and \( \lambda/6 \) are incident on a metal surface. The stopping potential for these wavelengths are given as \( V_1 \), \( V_2 \), and \( V_3 \), respectively. If the work function of the metal is \( \phi \), calculate the work function using the given wavelengths. The photoelectric equation is given by: \[ E_k = h \nu - \phi \] where:
\( E_k \) is the kinetic energy of the emitted electrons (which is related to the stopping potential),
\( h \) is Planck's constant,
\( \nu \) is the frequency of the incident light,
\( \phi \) is the work function of the metal.The frequency \( \nu \) is related to the wavelength \( \lambda \) by the equation: \[ \nu = \frac{c}{\lambda} \] where \( c \) is the speed of light.
- The difference between threshold wavelengths for two metal surfaces \( A \) and \( B \) having work functions \( \phi_A = 9 \, \text{eV} \) and \( \phi_B = 4.5 \, \text{eV} \) is: \[ \text{(Given: } h c = 1242 \, \text{eV nm)} \]
- The maximum kinetic energy of the photoelectrons varies.
- When the work function of a metal increases, maximum kinetic energy of emitted photoelectrons
- The maximum velocity of the photoelectron emitted by the metal surface is \( v \). Charge and mass of the photoelectron is denoted by \( e \) and \( m \) respectively. The stopping potential in volt is
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Concepts Used:
Photoelectric Effect
When light shines on a metal, electrons can be ejected from the surface of the metal in a phenomenon known as the photoelectric effect. This process is also often referred to as photoemission, and the electrons that are ejected from the metal are called photoelectrons.
Photoelectric Effect Formula:
According to Einstein’s explanation of the photoelectric effect :
The energy of photon = energy needed to remove an electron + kinetic energy of the emitted electron
i.e. hν = W + E
Where,
- h is Planck’s constant.
- ν is the frequency of the incident photon.
- W is a work function.
- E is the maximum kinetic energy of ejected electrons: 1/2 mv².
Laws of Photoelectric Effect:
- The photoelectric current is in direct proportion to the intensity of light, for a light of any given frequency; (γ > γ Th).
- There exists a certain minimum (energy) frequency for a given material, called threshold frequency, below which the discharge of photoelectrons stops completely, irrespective of how high the intensity of incident light is.
- The maximum kinetic energy of the photoelectrons increases with the increase in the frequency (provided frequency γ > γ Th exceeds the threshold limit) of the incident light. The maximum kinetic energy is free from the intensity of light.
- The process of photo-emission is an instantaneous process.