Suppose that we double the electrical power flowing into the filament of an incandescent bulb. By what factor will the most probable photon energy $\varepsilon_{p}$ increase?
A) $2^{1 / 4}$
B) $2^{1 / 3}$
C) $2^{1 / 2}$
D) 2
E) 4
F) 8
G) 16

Question

Quizplus · Accepted Answer

The most probable photon energy $\varepsilon_{p}$ is proportional to the temperature $T$ of the filament. The power $P$ radiated by a black body is proportional to $T^4$. Doubling the power means $P \propto (2T)^4$, so $T$ increases by a factor of $2^{1/4}$. Thus, $\varepsilon_{p}$ increases by $2^{1/4}$.

Suppose That We Double the Electrical Power Flowing into the Filament