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The wavelength of a 1 keV photon is 1.24 × 10–9 m. What is the frequency of 1 MeV photon ? [1991]
  • a)
    1.24 × 1015
  • b)
    2.4 × 1020
  • c)
    1.24 × 1018
  • d)
    2 × 4 × 1023
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
The wavelength of a 1 keV photon is 1.24 × 10–9 m. What is...
Here, hc/λ  = 103 eV and hv = 106 eV
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The wavelength of a 1 keV photon is 1.24 × 10–9 m. What is...
Understanding Photon Energy and Frequency
To find the frequency of a 1 MeV photon, we can use the relationship between energy (E), frequency (ν), and Planck’s constant (h). The formula is:
\[ E = h \cdot \nu \]
Where:
- \( E \) is the energy in joules,
- \( h \) is Planck’s constant (approximately \( 6.626 \times 10^{-34} \, \text{Js} \)),
- \( \nu \) is the frequency in hertz (Hz).

Converting MeV to Joules
1 MeV (mega electronvolt) is equivalent to \( 1.602 \times 10^{-13} \) joules. Thus, for a 1 MeV photon:
\[ E = 1 \, \text{MeV} = 1.602 \times 10^{-13} \, \text{J} \]

Calculating Frequency
Now, we can calculate the frequency using the formula:
\[ \nu = \frac{E}{h} \]
Substituting the values:
\[ \nu = \frac{1.602 \times 10^{-13}}{6.626 \times 10^{-34}} \]
Calculating this gives:
\[ \nu \approx 2.42 \times 10^{20} \, \text{Hz} \]

Final Answer
Rounding this to two significant figures, we get:
\[ \nu \approx 2.4 \times 10^{20} \, \text{Hz} \]
Thus, the frequency of a 1 MeV photon is approximately \( 2.4 \times 10^{20} \, \text{Hz} \), which corresponds to option **B**.
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The wavelength of a 1 keV photon is 1.24 × 10–9 m. What is the frequency of 1 MeV photon ? [1991]a)1.24 × 1015b)2.4 × 1020c)1.24 × 1018d)2 × 4 × 1023Correct answer is option 'B'. Can you explain this answer?
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