Why do we use prefixes like nano, pico, kilo, and micro?

1 Answer
Aug 14, 2017

For convenience... We would not want to write

#"0.000000001 m"#

to express one billionth of a meter. That just doesn't look nice, and it is preferable to write

#"1 nm"#,

1 nanometer, as there are #10^9# nanometers in one meter; they are one billionth of a meter in physical size. Of course, we could also have, in scientific notation, written

#10^(-9) "m"#,

which is OK, but as chemists, we prefer to have our numbers be roughly between #0.01# and #100#, and for them to be standardized (be made common usage) among us. They tend to be dependent on context.

One tends to use #"nm"# to describe UV and visible wavelengths, i.e. #"400 - 700 nm"# describes the visible range of light. We'd rather not say #4.00 xx 10^(-7) "m" - 7.00 xx 10^(-7) "m"#, which is awkward.

Common uses:

  • #"nm"#: wavelengths of visible light
  • #"pm"#: bond length, atomic radii
  • #"km"#: driving distances
  • #mu"m"#: bacteria size