Physics

Problem

An LED consumes

2.0\,\text{W}

of electrical power, but only

25\%

of that power is emitted as monochromatic blue light of wavelength

450\,\text{nm}

. If a camera shutter is open for

1/60\,\text{s}

, how many blue photons are emitted during the exposure? a)

7.5\times10^{16}

1.1\times10^{18}

1.9\times10^{16}

5.7\times10^{16}