Asked in Premeth MDCAT 2025 LR-04 — Electromagnetism, Transition Elements 2025Moderate

If a proton, alpha particle, and photon moving with the same velocity enter a uniform magnetic field, then which particle will deflect more?

Correct answer: A. Proton

  • A. Proton
  • B. Alpha particle
  • C. Photon
  • D. All of these options are correct

Explanation

The magnitude of deflection depends upon two factors: The mass (m) of the ion - the lighter it is the more it will be deflected. The charge (z) on the ion - ions with 2+ charges are deflected more than 1+. These two factors are combined into the mass-to-charge ratio (m/z). The photon is electrically neutral and thus will not deflect in a magnetic field. Protons will deflect the most as they have 1 amu for +1 charge, while the alpha particle will deflect less as they have 4 amu for +2 charge. Since the protons have the smallest mass-to-charge ratio their deflection will be greatest.

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About Charged Particle in a Magnetic Field

A charged particle moving through a magnetic field experiences the Lorentz force, which is perpendicular to both its velocity and the field. The motion may be circular or helical, with questions involving radius, angular frequency, time period, and work done. A stationary charge feels no magnetic force.

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