Ultraviolet light in the sun has a disinfectant effect. When not using a cutting board, the cutting board should be placed in the sun. This will not only eliminate bacteria but also prevent bacteria from multiplying, because the cutting board will become dry in the sun. Sunlight contains an electromagnetic wave with a wavelength shorter than that of visible light. It is located on the outer side of violet light in red, orange, green, blue-violet, and seven-color light. We call it ultraviolet light. Ultraviolet rays can destroy the nucleic acids of bacteria and viruses (life is one of the basic substances, which plays a decisive role in the growth, genetics, and mutation of living organisms), decomposes, degenerates, loses normal functions, and can also affect the activity of enzymes. The normal metabolic synthesis of proteins and nucleic acids prevents the death or mutation of bacteria and viruses. Therefore, we can claim that UV is a "natural bactericide" without exaggeration.