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Standard XII

Chemistry

Nature of Electromagnetic Radiation

A bulb emits ...

Question

A bulb emits light of wavelength 198 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. The number of photons emitted per second is $10^{x}$ . Take $h = 6.6 \times 10^{- 34}$ . The value of $x$ is

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Solution

Energy of the bulb = 100 watt = 100 J per second
Percentage of energy emitted as light = 10%
Energy emitted as light per second = 10 J
Energy of the photon = $h ν$
$= \frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{1980 \times 10^{- 10}}$

$= 1 \times 10^{- 18}$ J

Number of photons $= \frac{Total energy emitted per second}{Energy of one photon}$

$= \frac{10}{10^{- 18}}$ = $10^{19}$

Hence, the value of $x = 19$

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A bulb emits light of wavelength 198 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. The number of photons emitted per second is 10x. Take h=6.6×10−34. The value of x is

A bulb emits light of wavelength 198 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. The number of photons emitted per second is $10^{x}$ . Take $h = 6.6 \times 10^{- 34}$ . The value of $x$ is