Electrons of mass m and charge e are accelerated through a potential difference V and strike the target. The maximum speed of these electrons is:
Correct answer: D. √(2eV/m)
- A. √(e²/m)
- B. eV/m
- C. eV²/m
- D. √(2eV/m)
Explanation
Work Done by the Electric Field: The work done (W) by the electric field on the electron is equal to the charge of the electron (e) multiplied by the potential difference (V): W = eVKinetic Energy of the Electron: The work done is converted into the kinetic energy (KE) of the electron. The kinetic energy is given by: KE = (1/2)mv²Equating Work and Kinetic Energy: According to the work-energy theorem, the work done is equal to the change in kinetic energy: eV = (1/2)mv²Solving for Velocity (v): Now, we solve for the velocity (v): 2eV = mv² v² = 2eV / m v = √(2eV / m)
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Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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