c
(C) પ્લાન્કમાં સિદ્ધાંત મુજબ,  \(E = \frac{{nhc}}{\lambda }\)  \((n =\) ફોટોનની સંખ્યા\()\) બલ્બ ની ઉર્જા

\( (E)\,\, = \,\,\frac{{150 \times 8}}{{100}}\,\, = \,\,12w\,\, = \,\,12\,\,J{s^{ - 1}}\,\,(\,\,\because \,\,\,1W\,\, = \,\,1\,\,J{s^{ - 1}})  \)

\(  \lambda \,\, = \,\,4500\,\mathop A\limits^o    = 4500 \times {10^{ - 10}}\,m,\,\,\,C\,\, = \,\,3 \times {10^8}\,m{s^{ - 1}},\,\,h\,\, = \,\,6.62 \times {10^{ - 34}}\,Js  \)

\(  12\,J{s^{ - 1}}\,\, = \,\,\frac{{n \times (6.62 \times {{10}^{ - 34}}\,J) \times (3 \times {{10}^8}\,m{s^{ - 1}})}}{{(4500 \times {{10}^{ - 10}}\,m)}}\,\,\,\, \)

\(\Rightarrow \,\,\,n\,\, = \,\,\frac{{(12\,J{s^{ - 1}}) \times (45 \times {{10}^{ - 8}}\,m)}}{{(6.62 \times {{10}^{ - 34}}\,Js) \times (3 \times {{10}^8}\,m{s^{ - 1}})}}\,\, = \,\,2.72 \times {10^{19}}\,{s^{ - 1}} \)