What unit is used to measure and express wavelengths?

What unit is used to measure and express wavelengths?

• A. Nanometer
• B. Micrometer
• C. Millimeter
• D. Centimeter

Answer: (A)

Wavelengths of light are described in very small units, so using a unit that keeps the numbers convenient is essential. The nanometer (one-billionth of a meter) does just that, giving values in the hundreds of nanometers for visible light (roughly 380–750 nm) and still practical values for nearby wavelengths. This makes it easy to talk about color and optical properties—for example, blue light is around 450 nm and red light around 650–700 nm. While micrometers are sometimes used for infrared wavelengths, nanometers are the standard unit for expressing most wavelengths in optics because they keep the numbers manageable and directly relate to visible colors.

Wavelengths of light are described in very small units, so using a unit that keeps the numbers convenient is essential. The nanometer (one-billionth of a meter) does just that, giving values in the hundreds of nanometers for visible light (roughly 380–750 nm) and still practical values for nearby wavelengths. This makes it easy to talk about color and optical properties—for example, blue light is around 450 nm and red light around 650–700 nm. While micrometers are sometimes used for infrared wavelengths, nanometers are the standard unit for expressing most wavelengths in optics because they keep the numbers manageable and directly relate to visible colors.