Question

a laser emits photons continuously at a rate of 6.8*1016/s. if the wavelength of the photons is 641 nm, what is the laser power in mw?

Answer 1

The laser power is 27,69 mW.

Power= energy/sec = J/s

Photon energy= hf= hc /wavelength

# of photons/sec = power/ photon energy= rate of emission

Photon Energy= ( 6.63 × $10^{-34}$) × 3×$10^{8}$ / 6.8×$10^{16}$ ≈ 3.147 ×$10^{-42}$ J

This should be ignored. It is part of the units and not the equation.

Power/3.147 × $10^{-42}$ = 8.8 × $10^{26}$ $s^{-1}$

Power= 8.8 × $10^{-26}$- 3.147 × $10^{-42}$ J= 0 .02769 W = 27.69 mW

How is laser power determined?

The energy levels of the electrons in the atoms of the material used to create the laser beam—often referred to as the "lasing" material—determine the intensity of the laser beam. The wavelength of the light generated by the lasing material has an inverse relationship with the energy level of the photons that are created by it.

Can a laser's power be increased?

The intensity of the light increases with the amount of energy used to excite those atoms in the laser. It almost resembles dialing up the sound system's volume control. However, if you turn that level up too loud, you run the danger of harming your hearing or the sound system itself.

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