A) \[1.5\times {{10}^{20}}\]
B) \[6\times {{10}^{18}}\]
C) \[62\times {{10}^{20}}\]
D) \[3\times {{10}^{19}}\]
Correct Answer: A
Solution :
[a] Give that, only 25% of 200W converter electrical energy into light of yellow color \[\left( \frac{hc}{\lambda } \right)\times N=200\times \frac{25}{100}\] Where N is the No. of photons emitted per second, h = plank's constant, c, speed of light. \[N=\frac{200\times 25}{100}\times \frac{\lambda }{hc}\] \[=\frac{200\times 25\times 0.6\times {{10}^{-6}}}{100\times 6.2\times {{10}^{-34}}\times 3\times {{10}^{8}}}=1.5\times {{10}^{20}}\]
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