Asked in FBISE Physics 2022 — Paper 2 2022

Which particle has the shortest wavelength, if all are Having the same velocity?

Correct answer: D. a- particle

  • A. Electron
  • B. Proton
  • C. Neutron
  • D. a- particle

Explanation

The particle with the shortest wavelength, when all particles have the same velocity, is the one with the highest mass. This is because the de Broglie wavelength (\lambda) of a particle is inversely proportional to its momentum (p), which is the product of mass (m) and velocity (v). The relationship is given by the equation:λ= h/p = h/mvwhere (h) is Planck's constant. So, for a constant velocity, the greater the mass of the particle, the smaller the wavelength.The mass of the particles in increasing order is: electron < proton ≈ neutron < alpha particle. Therefore, the wavelengths in decreasing order are: electron > proton ≈ neutron > alpha particle. So, the alpha particle has the shortest wavelength among the given particles when they all move with the same velocity.

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The particle model treats light as photons with energy E equals hf and momentum related to wavelength. Questions involve the photoelectric effect, work function, threshold frequency, stopping potential and photon energy, while distinguishing particle behaviour from the wave description of interference and diffraction.

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