Question

Calculate the number of photons emitted per second by a 10 W sodium vapour lamp. Assume that 60% of the consumed energy is converted into light. Wavelength of sodium light = 590 nm

Answer 1

Answer:

Explanation:

apply :

60 /100 * 10 J = n h c / wavelength

h= 6.626*10^-34

c = 3*10^8

wavelength = 590*10^-9

6 = n * 6.626*10^-34*3*10^8/590*10^-9

n = 1.78*10^19

Answer 2

The number of emitted photons is $1.77 \times 10^{19}$.

Explanation:

In the question, it is given:

Sodium vapour lamp’s power, $P=10 \mathrm{W}$

Sodium light’s wavelength, $\lambda=590 \mathrm{nm}$

The bulb consumes the electric energy in one second = 10 J

Quantity of energy transformed into light = 60 %

Therefore, the light formed from the converted energy = $10 \times 60100=6 J$.

For emitting photon from the sodium atom, the required energy is

$E^{\prime}=h c \lambda E^{\prime}$

$=6.63 \times 10-17 J \times 3590$

Number of emitted photons,

$n=6 \times 3 \times 5906.63 \times 1017$

$n=1.77 \times 1019$