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2. structure of atom — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistry2. structure of atom1 Mark
MCQ
A $124\ W$ bulb converts only $15\ \%$ of the energy supplied to it into visible light of wavelength $640\  nm$ . How many photons are emitted by the light bulb in one second
  • A
    $4 \times 10^{19}$
  • ✓
    $6 \times 10^{19}$
  • C
    $8 \times 10^{18}$
  • D
    $3 \times 10^{19}$ photon
✓

Answer

Correct option: B.
$6 \times 10^{19}$
b
$\frac{{124 \times 0.15}}{{\frac{{1240}}{{640}} \times 1.6 \times {{10}^{ - 19}}}}$

$ = \frac{{124 \times 640}}{{124 \times 16}} \times {10^{19}} \times 0.15$

$ = 6 \times {10^{19}}$

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