The prefix 'femto' in SI units represents a factor of: MCQ with Answer and Explanation

The SI prefix 'femto' denotes a factor of 10⁻¹⁵. This is standardized by the International Bureau of Weights and Measures. Common prefixes: pico (10⁻¹²), femto (10⁻¹⁵), atto (10⁻¹⁸), nano (10⁻⁹). Femtometer (10⁻¹⁵ m) is used in nuclear physics to measure atomic nuclei sizes. Exam tip: Remember the sequence: pico, femto, atto for decreasing scales. This question tests fundamental knowledge of SI prefixes essential for unit conversions in competitive examinations.