LED lights are ruing “whiter than white” detergent claims

LED lighting is great. The right bulb gives the same warm incandescent glow you love from a fraction of the energy. But there’s a downside: while LEDs make cities look awesome, the most common type of LED lighting dims the ultraviolet trick laundry detergents use to make white clothes look whiter. The future is bright, but it’s also kind of dingy. There’s some fascinating science going on here. Many laundry detergents contain fluorescent whitening agents, or FWAs, which absorb ultraviolet light and re-emit it as a visible blue wavelength. This slightly bluish tinge helps overpower the yellowish hue of, say, a well-worn undershirt, making that nasty old rag look radiant and white.