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JEE · NEET Previous Year Question

$The wavelength of a 1 keV photon is 1.24 \times 1 0^{- 9} m . What is the frequency of 1 MeV photon?$

Topic: NEET PYQ

Answer: B. Full step-by-step solution below.

A $1.24 \times 1 0^{15}$
B $2.4 \times 1 0^{20}$
C $1.24 \times 1 0^{18}$
D $2.4 \times 1 0^{23}$

Correct answer: B

Solution

(b) Here, \frac{hc}{λ} = 1 0^{3} eV and h ν = 1 0^{6} eV Hence, ν = \frac{1 0 ^{3} c}{λ} = \frac{1 0 ^{3} \times 3 \times 1 0 ^{8}}{1.24 \times 1 0 ^{- 9}} = 2.4 \times 1 0^{20} Hz

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