Final answer:
The fading of bright colors in fabrics like a blue shirt over time is due to photon energy affecting the dye molecules. Blue and violet dyes tend to be more resilient as they reflect high-energy photons that can cause molecular damage, while dyes that absorb such photons, like reds and greens, fade more quickly.
Step-by-step explanation:
Why Bright Colors Fade Over Time
When you buy a brightly colored shirt and find that it fades after multiple washes, it's due to the photon energy absorbed by the dye molecules in the fabric. Sunlight and the mechanical action during washing can wear down these complex molecules. However, there is a difference in how various colored dyes respond to light, particularly sunlight, due to the photon energy associated with different colors of light.
Blue and violet dyes are less susceptible to fading because these colors reflect high-energy blue and violet photons rather than absorbing them. This means they incur less molecular damage from the light. Dyes absorbing these more energetic photons, like red and green, will fade quicker as their molecular structure is more likely to be broken down over time. Therefore, the bright blue shirt fades as the dye molecules degrade due to repeated washing and exposure to light, especially if the light is intense and rich in high-energy photons.
Items like posters displayed in sunlight illustrate this well, as the reds, yellows, and greens fade before the blues and violets. The higher energy of blue and violet photons can break up the weakly bound molecules in these other colors, leading to a more rapid fading process. Additionally, the durability of some dyes under sunlight and washing, as reflected in the remaining vibrancy of blue colors in fabrics, owes to their reflective properties against higher energy photons in the light spectrum.