Home >> Science & Nature >> Science

How to Express Nanometers

While objects and distances in the human world can be described in terms of meters or kilometers, it is inconvenient to use these scales to describe extremely small distances. A nanometer is a small unit of measuring distance. It is equivalent to one billionth of a meter. Thankfully, the International System of Units (SI being the French acronym) allows you to easily understand, convert and express distances of this scale.

Scientific Notation
- In order to express extremely small or extremely large numbers, it is important to understand the conventions of scientific notation. Scientific notation refers to the expression of numbers by powers of ten. For example, instead of writing 0.05, you can express this by writing 5 x 10^-2. Likewise, 500 could be expressed 5 x 10^2. If there are multiple significant digits, you can express these in the form of decimals. For example, 0.053 is expressed as 5.3 x 10^-2. Likewise, 530 is expressed as 5.3 x 10^2.
SI Units
- In order to streamline and standardize the expression of units, the SI conventions associate a prefix with a power of ten. The "nano" prefix is equivalent to 10^-9. Therefore, one nanometer is equivalent to 0.000000001 meters. The first three positive and negative powers of ten have SI equivalents. After both 10^3 and 10^-3, however, SI units correspond to every third power of ten. For example, milli is 10^-3, micro is 10^-6, nano is 10^-9 and pico is 10^-12. In order to express something outside of these powers, decimals are used. For example, a measurement of 0.00000000001 meters is typically expressed as 0.001 nanometers. Each SI prefix has a symbolic abbreviation. Nanometers are expressed as "nm."
Examples of the Nanometer Scale
- Nanometers are often used to describe the size of atoms or molecules. Depending on the type of bond involved between atoms, atoms of iodine may have radii between 0.1333 and 0.216 nm. Larger molecules are also expressed on a nanometer scale. For example, a DNA molecule has a diameter of approximately 2.5 nm. Nanometers are also used to describe wavelengths of visible light. Visible light has wavelengths between 400 and 700 nm.
The Angstrom
- Many distances of an atomic scale are less than one nanometer. Sometimes these distances are expressed using a unit called the angstrom. The angstrom is not an official SI unit but is frequently used in relation to other SI units. An angstrom is equivalent to 0.1 nm. This scale is so prevalent in the atomic world that the angstrom is common in physics and chemistry literature.

Science