For melanin, how does absorption change as wavelength increases?

• A. Increases
• B. Decreases
• C. Remains constant
• D. Fluctuates

Answer: (B)

Melanin absorbs light more strongly at shorter wavelengths and its absorption tapers off as wavelength gets longer. This happens because the pigments in melanin have higher absorption coefficients in the UV and blue end of the spectrum, and the probability of photon absorption decreases with increasing photon wavelength into the visible and near-infrared. So as wavelength increases, melanin absorbs less light. That’s why the correct idea is that absorption decreases with longer wavelength. The other options don’t fit this trend: absorption does not rise with wavelength, remain constant, or fluctuate without a consistent pattern across the spectrum.