Amplitude Calculation in Helium-Neon Laser Beam
What is the amplitude of the magnetic fields inside a beam produced by a helium-neon laser?
Given a helium-neon laser producing a beam of diameter 1.75 mm and delivering 2.00 × 10^18 photons/s, each with a wavelength of 633 nm, calculate the amplitude of the magnetic fields inside the beam.
Amplitude of Magnetic Fields Calculation
A helium-neon laser producing a beam with a diameter of 1.75 mm and delivering 2.00 × 10^18 photons/s emits each photon with a wavelength of 633 nm. To calculate the amplitude of the magnetic fields inside the beam, we can utilize the intensity and amplitude of the electromagnetic wave.
The intensity (I) of an electromagnetic wave is proportional to the amplitude of its electric and magnetic fields (E and B), as shown by the equation:
I = cε₀E²
Given data:
- Diameter of the beam (d) = 1.75 mm = 1.75 × 10^-3 m
- Number of photons emitted per second (N) = 2.00 × 10^18 photons/s
- Wavelength of each photon (λ) = 633 nm = 633 × 10^-9 m
The energy of each photon is:
E = hc/λ
Calculating the energy gives a value of approximately 3.13 × 10^-19 J. The intensity of the beam is approximately 2.61 × 10^3 W/m^2, resulting in an amplitude of the magnetic fields inside the beam of about 0.008 Tesla (T).
Therefore, the amplitude of the magnetic fields inside the beam produced by the helium-neon laser is approximately 0.008 T.