Q143 / 200 · NEET 2010 (Screening) · Physics

A source $\mathrm{S}_1$ is producing, $10^{15}$ photons/s of wavelength $5000 Å$. Another source $S_2$ is producing $1.02 \times 10^{15}$ photons per second of wavelength $5100 Å$. Then, (power of $\left.S_2\right) /\left(\right.$ power of $S_1$ ) is equal to

  • Correct answer
    A
    1.00
  • B
    1.02
  • C
    1.04
  • D
    0.98

Solution

Number of photons emitted per second $$ \begin{array}{cc} \quad \mathrm{n}=\frac{\mathrm{P}}{\left(\frac{\mathrm{hc}}{\lambda}\right)} \\ \therefore \quad \mathrm{P}=\frac{\mathrm{nhc}}{\lambda} \\ \Rightarrow \frac{\mathrm{P}_2}{\mathrm{P}_1}=\frac{\mathrm{n}_2 \lambda_1}{\mathrm{n}_1 \lambda_2}=\frac{1.02 \times 10^{15} \times 5000}{10^{15} \times 5100}=1 \end{array} $$

Hence, the correct answer is option: 'A'.

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