Longer wavelengths have lower absorption and higher energy.

• A. Higher absorption and lower energy
• B. Lower absorption and higher energy
• C. Higher absorption and higher energy
• D. Lower absorption and lower energy

Answer: (B)

Longer wavelengths carry less energy per photon, since energy per photon is E = h c / λ. Absorption by pigment or tissue varies with wavelength, and in laser hair removal longer wavelengths tend to be absorbed less by melanin, meaning lower absorption for hair pigment at longer wavelengths. Because energy decreases with increasing wavelength, you can’t have higher energy at longer wavelengths. The statement mixes these ideas, so it isn’t accurate. The best match is the choice that lists both lower absorption and lower energy, since both photon energy and pigment absorption tend to decrease as wavelength increases.