The wavelength of a 1 keV photon is 1.24 × 10⁻⁹ m. What is the frequency of 1 MeV photon? (a) 1.24 × 10¹⁵ (b) 2.4 × 10²⁰ (c) 1.24 × 10¹⁸ (d) 2.4 × 10²³

Answer: (b). For the 1 keV photon: ν₁ = (c)/(λ) = 3 × 10⁸1.24 × 10⁻⁹ = 2.42 × 10¹⁷ Hz. E = hν ⇒ ν ∝ E; 1 MeV is 1000 times 1 keV. ν₂ = 1000 × 2.42 × 10¹⁷ ≈ 2.4 × 10²⁰ Hz So the answer is (b).

The wavelength of a 1 keV photon is 1.24 × 10⁻⁹ m. What is the… | NEET 1991 (AIPMT)

Q46NEET 1991 · AIPMTEasy

Photons: Energy, Momentum & Radiation Pressure

The wavelength of a 1 keV photon is $1.24 \times 10^{-9}$ m. What is the frequency of 1 MeV photon?

Show answer and solution

Answer: (b)

For the 1 keV photon: $\nu_1 = \frac{c}{\lambda} = \frac{3 \times 10^{8}}{1.24 \times 10^{-9}} = 2.42 \times 10^{17}\text{ Hz}$ .
$E = h\nu \Rightarrow \nu \propto E$ ; 1 MeV is 1000 times 1 keV.
$\nu_2 = 1000 \times 2.42 \times 10^{17} \approx 2.4 \times 10^{20}\text{ Hz}$
So the answer is (b).

Report a mistake

Photons: Energy, Momentum & Radiation Pressure question from NEET 1991 (AIPMT)

More questions on Photons: Energy, Momentum & Radiation Pressure