Find the number of photons emitted per second by a $100\, W$ red light source. Assume for simplicity that the average wavelength of each photon is $694\, nm$.

  • A
    $3.49 \times 10^{20}$
  • B
    $4.49 \times 10^{20}$
  • C
    $3.49 \times 10^{18}$
  • D
    $4.49 \times 10^{18}$

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The energy of a photon with a wavelength of $\lambda = 4000 \ \mathring{A}$ is equal to ........ Joules.

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If the energy of a photon corresponding to a wavelength of $6000 \mathring{A}$ is $3.2 \times 10^{-19} \ J$,the photon energy for a wavelength of $4000 \mathring{A}$ will be . . . . . . .

The frequency of a photon having energy $100 \ eV$ is $(h = 6.6 \times 10^{-34} \ J \cdot s)$.

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Write the equation for the energy of a photon.

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