A photocathode that has a work function of $2.4 \mathrm { eV }$ is illuminated with monochromatic light having photon energy $3.5 \mathrm { eV }$. What is the wavelength of this light? $\left( c = 3.00 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } , h = 6.626 \times 10 ^ { - 34 } \mathrm {~J} \right.$. $\mathrm { s } , 1 \mathrm { eV } = 1.60 \times 10 ^ { - 19 } \mathrm {~J}$ )
A) $350 \mathrm {~nm}$
B) $300 \mathrm {~nm}$
C) $410 \mathrm {~nm}$
D) $330 \mathrm {~nm}$
E) $380 \mathrm {~nm}$

Question

Quizplus · Accepted Answer

The wavelength of the light can be calculated using the formula $\lambda = \frac{hc}{E}$, where $h$ is Planck's constant, $c$ is the speed of light, and $E$ is the energy of the photon. Given $E = 3.5 \mathrm{eV} = 3.5 \times 1.60 \times 10^{-19} \mathrm{J}$, $h = 6.626 \times 10^{-34} \mathrm{J \cdot s}$, and $c = 3.00 \times 10^8 \mathrm{m/s}$, substituting these values gives $\lambda \approx 350 \mathrm{nm}$.

A Photocathode That Has a Work Function Of 2.4eV2.4 \mathrm { eV }2.4eV

A Photocathode That Has a Work Function Of $2.4 \mathrm { eV }$