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The wavelength of a 1 keV photon is 1.24×10⁻⁹ m. What is the frequency of a 1 MeV photon?

Asked in AIPMT 1991 · Photon energy, momentum and mass

Answer: (2) 2.4×10²⁰ Hz

Step-by-step solution

The given wavelength fixes the constant: for the 1 keV photon, (hc)/λ=10³ eV with λ=1.24×10⁻⁹ m.

A 1 MeV photon has 10³ times the energy, so h u=10⁶ eV=10³×(hc)/λ.

Dividing by h: u=(10³c)/λ.

u=(10³×3×10⁸)/(1.24×10⁻⁹)=2.4×10²⁰ Hz.

Why the other options are wrong

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