Question.
A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57μm. Calculate the rate of emission of quanta per second
A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57μm. Calculate the rate of emission of quanta per second
Solution:
Power of bulb, $P=25 \mathrm{Watt}=25 \mathrm{~J} \mathrm{~s}^{-1}$
Energy of one photon, $E=h v=\frac{h c}{\lambda}$
Substituting the values in the given expression of $E$ :
$E=\frac{\left(6.626 \times 10^{-34}\right)\left(3 \times 10^{8}\right)}{\left(0.57 \times 10^{-6}\right)}=34.87 \times 10^{-20} \mathrm{~J}$
$\left.E=34.87 \times 10^{-20}\right]$
Rate of emission of quanta per second
$=\frac{25}{34.87 \times 10^{-20}}=7.169 \times 10^{19} \mathrm{~s}^{-1}$
Power of bulb, $P=25 \mathrm{Watt}=25 \mathrm{~J} \mathrm{~s}^{-1}$
Energy of one photon, $E=h v=\frac{h c}{\lambda}$
Substituting the values in the given expression of $E$ :
$E=\frac{\left(6.626 \times 10^{-34}\right)\left(3 \times 10^{8}\right)}{\left(0.57 \times 10^{-6}\right)}=34.87 \times 10^{-20} \mathrm{~J}$
$\left.E=34.87 \times 10^{-20}\right]$
Rate of emission of quanta per second
$=\frac{25}{34.87 \times 10^{-20}}=7.169 \times 10^{19} \mathrm{~s}^{-1}$