A Photocathode Having a Work Function Of $2.8 \mathrm { eV }$

Multiple Choice

A photocathode having a work function of $2.8 \mathrm { eV }$ is illuminated with monochromatic electromagnetic radiation whose photon energy is $4.0 \mathrm { eV }$ . What is the threshold (cutoff) frequency for photoelectron production? $\left( 1 \mathrm { eV } = 1.60 \times 10 ^ { - 19 } \mathrm {~J} , h = 6.626 \times 10 ^ { - 34 } \mathrm {~J} \cdot \mathrm { s } \right)$

A) $8.6 \times 10 ^ { 14 } \mathrm {~Hz}$
B) $2.9 \times 10 ^ { 14 } \mathrm {~Hz}$
C) $6.8 \times 10 ^ { 14 } \mathrm {~Hz}$
D) $9.7 \times 10 ^ { 14 } \mathrm {~Hz}$
E) $7.7 \times 10 ^ { 14 } \mathrm {~Hz}$