A certain helium-neon laser pointer, emitting light with a wavelength of 632 nm, has a beam with an intensity of 825 W/m2 and a diameter of 2.80 mm. How many photons are emitted by the laser pointer every second?

Question

contestada

Respuesta :

aristocles aristocles · Answer 1 · 2019-07-17T03:52:24+02:00

Answer:

[tex]N = 1.62 \times 10^{15}[/tex]

Explanation:

Energy of each photon is given as

[tex]E = \frac{hc}{\lambda}[/tex]

here we will have

[tex]\lambda = 632 nm[/tex]

now we will have

[tex]E = \frac{(6.626\times 10^{-34})(3 \times 10^8)}{632 \times 10^{-9}}[/tex]

[tex]E = 3.14 \times 10^{-19} J[/tex]

now let say there is N number of photons per second

so power due to photons is

[tex]P = N(3.14 \times 10^{-19})[/tex]

now intensity is given as power received per unit area

so we have

[tex]I = \frac{P}{A}[/tex]

[tex]825 = \frac{N(3.14 \times 10^{-19})}{\pi (1.40 \times 10^{-3})^2}[/tex]

[tex]825 = N(5.11 \times 10^{-14})[/tex]

[tex]N = 1.62 \times 10^{15}[/tex]