Question

Neon gas is generally used in the signboards. If it emits strongly at 616 nm

Calculate:

(a) The frequency of emission,

(b) Distance travelled by this radiation in 30 s

(c) The energy of quantum and

(d) The number of quanta present, if it produces 2 J of energy.

Answer 1

(a) The frequency of emission is $\frac{c}{\lambda }=\frac{3.0\times {10}^8}{616\times {10}^{-9}}=4.87\times {10}^{14}$.

(b) The distance travelled in 30 s is

$d=t\times \lambda \times \nu$

$=30\times 616\times {10}^{-9}\times 4.87\times {10}^{14}=9.0\times {10}^{9}m$.

(c) The energy of quanta is $E=h\nu =6.626\times {10}^{-34}\times 4.87\times {10}^{14}=3.227\times {10}^{-19}J$.

(d) The number of quanta in 2J of energy is $\frac{2}{3.227\times {10}^{-19}}=6.2\times {10}^{18}$ photons.