Neon gas is generally used in sign boards. If it emits strongly at $616 \, nm$,calculate $(a)$ the frequency of emission,$(b)$ distance traveled by this radiation in $30 \, s$,$(c)$ energy of a quantum,and $(d)$ number of quanta present if it produces $2 \, J$ of energy.

(D) Wavelength of radiation emitted $(\lambda) = 616 \, nm = 616 \times 10^{-9} \, m$ (Given).
$(a)$ Frequency of emission $(v) = \frac{c}{\lambda} = \frac{3.0 \times 10^{8} \, m/s}{616 \times 10^{-9} \, m} = 4.87 \times 10^{14} \, s^{-1}$.
$(b)$ Distance traveled by radiation in $30 \, s = \text{velocity} \times \text{time} = (3.0 \times 10^{8} \, m/s) \times (30 \, s) = 9.0 \times 10^{9} \, m$.
$(c)$ Energy of a quantum $(E) = hv = (6.626 \times 10^{-34} \, J \cdot s) \times (4.87 \times 10^{14} \, s^{-1}) = 3.227 \times 10^{-19} \, J$.
$(d)$ Number of quanta in $2 \, J$ of energy $= \frac{\text{Total Energy}}{\text{Energy of one quantum}} = \frac{2 \, J}{3.227 \times 10^{-19} \, J} = 6.197 \times 10^{18} \approx 6.2 \times 10^{18}$ quanta.