Given:
The power of the laser is P = 2.99 W
The time duration is t = 3.5 s
The wavelength of the laser is
[tex]\begin{gathered} \lambda\text{ = 620.85 nm} \\ =620.85\text{ }\times10^{-9}\text{ m} \end{gathered}[/tex]Required: Number of photons emitted from the laser.
Explanation:
The energy of the laser is given by the formula
[tex]E=\frac{nhc}{\lambda}[/tex]
Here, n is the number of photons.
h is the Planck's constant whose value is
[tex]h\text{ = 6.6}\times10^{-34\text{ }}J\text{ s}[/tex]c is the speed of light whose value is
[tex]c=3\times10^8\text{ m/s}[/tex]The energy can also be calculated as
[tex]\begin{gathered} E=P\times t \\ =2.99\times3.5 \\ =10.465\text{ J} \end{gathered}[/tex]On substituting the values, the number of photons can be calculated as
[tex]\begin{gathered} n=\frac{E\lambda}{hc} \\ =\frac{10.465\times620.85\times10^{-9}}{6.6\times10^{-34}\times3\times10^8} \\ =3.28\times10^{19}\text{ } \end{gathered}[/tex]Final Answer: 3.28e19 photons are emitted.
