Final answer:
The laser beam in laser hair removal is attracted to the melanin pigment in the hair, which absorbs the laser light, heating up and consequently damaging the hair follicle to prevent hair regrowth. Laser wavelengths are chosen to be selectively absorbed by the targeted tissue while sparing surrounding skin.
Step-by-step explanation:
In laser hair removal, the laser beam is attracted to the pigment in the hair, known as melanin. The laser emits light that is absorbed by the melanin, which heats up and damages the hair follicle, inhibiting or delaying future hair growth. Lasers are chosen based on their wavelength so as to be efficiently absorbed by the melanin while minimizing absorption by surrounding tissue. This is possible due to the monochromatic and coherent nature of laser light, which allows for a precise focus on the hair follicle with minimal damage to surrounding skin.
Unlike broad-spectrum light sources, lasers generate a single wavelength of light that can be selectively absorbed by biological molecules with the corresponding absorption spectrum. For instance, water absorbs UV and IR light but is transparent to the visible spectrum, and hemoglobin in blood reflects red light but strongly absorbs in the UV spectrum. Therefore, it's crucial to select a laser with a wavelength that targets the specific molecule or tissue of interest.