Fabric brighteners, found in most detergents, don't clean clothes but enhance their appearance by making them glow. They work by absorbing ultraviolet light and emitting blue light, which masks yellowing and small stains. This effect is due to optical brighteners, a type of fluorescent chemical. While they make clothes look cleaner, they don't prevent fading caused by washing or sunlight. Historically, blue dye was used for similar effects. However, optical brighteners can be problematic in military settings as they are visible through night-vision goggles, leading to their ban in such contexts.

What is the primary function of fabric brighteners in detergents?

• To clean clothes thoroughly

• To remove stains completely

• To make clothes glow under UV light

• To enhance the appearance of existing dyes

How do optical brighteners work to enhance the appearance of clothes?

• By absorbing red light and emitting infrared light

• By absorbing blue light and emitting red light

• By absorbing UV light and emitting blue light

• By absorbing visible light and emitting UV light

Why do clothes treated with optical brighteners not appear to glow in normal lighting conditions?

• Because they absorb all visible light

• Because they only work in complete darkness

• Because the amount of brightener is too small to be visible

• Because they are designed to only work under UV light

What was the traditional method used to achieve the yellow-masking effect before optical brighteners?

• Adding red dye to laundry

• Using bleach

• Adding tiny amounts of blue dye

• Using vinegar

Why are detergents with optical brighteners banned in the military?

• They make clothes too bright in daylight

• They can be detected through night-vision goggles

• They cause clothes to deteriorate faster

• They are harmful to the environment