A Laser Pulse of Duration $25 \mathrm {~ms}$ Has a Total Energy Of

Multiple Choice

A laser pulse of duration $25 \mathrm {~ms}$ has a total energy of $1.4 \mathrm {~J}$ . If the wavelength of this radiation is 567 $\mathrm { nm }$ , how many photons are emitted in one pulse? $\left( c = 3.00 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } , h = 6.626 \times 10 ^ { - 34 } \mathrm {~J} \cdot \mathrm { s } \right)$

A) $9.9 \times 10 ^ { 19 }$
B) $1.6 \times 10 ^ { 17 }$
C) $3.2 \times 1017$
D) $4.8 \times 10 ^ { 19 }$
E) $4.0 \times 10 ^ { 18 }$