Neon gas is generally used in sign boards. If it emits strongly at 616 nm, calculate

(i) the frequency of emission.

(ii) distance travelled by this radiation is 30 s.

(in) energy of quantum.

(iv) number of quanta present if it produces 2 J of energy.

(i) Frequency ,v = c/ $\lambda $\

v= 3.0 x ${{10}^{8}}$ / 616 x ${{10}^{-9}}$ m = 4.870 x ${{10}^{14}}$ s

(ii) Distance travelled = speed x time = 3.0 x ${{10}^{8}}$m/s x 30 s = 9.0 x ${{10}^{9}}$

(iii) Energy of quantum (or photon) ,

E = hv = 6.626 x ${{10}^{-34 }}$ x 4.870 x ${{10}^{14}}$ s

= 32.268 x ${{10}^{-20}}$ J

(iv)Number of quanta present = total energy produced / energy of 1 quanta = 2 J / 32.27 x ${{10}^{-20}}$

= 6.2 x ${{10}^{19}}$ quanta