One nanometre is equal to which of the following?
- A.One millionth of a metre
- B.One billionth of a metre
- C.One thousandth of a metre
- D.One trillionth of a metre
Show answer
Correct answer: B. One billionth of a metre
Explanation
The correct answer is B, one billionth of a metre. The prefix nano stands for ten raised to the power minus nine, so one nanometre is one billionth of a metre, which is also ten angstrom, and nanotechnology is defined as work in the band of one to one hundred nanometres. Option A is wrong because one millionth of a metre is a micrometre or micron, the unit used for bacteria and for the thickness of a hair in older textbooks, and it is a thousand times larger than a nanometre. Option C is wrong because one thousandth of a metre is a millimetre, a length visible to the eye on any ruler. Option D is wrong because one trillionth of a metre is a picometre, a unit used for bond lengths inside a molecule and a thousand times smaller than a nanometre; the diameter of an atom is of the order of a hundred picometres.