Significant Figures (OCR AS Physics): Revision Note

Significant Figures

• Significant figures must be used when dealing with quantitative data

• Significant figures are the digits in a number that are reliable and absolutely necessary to indicate the quantity of that number

• There are some important rules to remember for significant figures

  • All non-zero digits are significant

  • Zeros between non-zero digits are significant

    • 4107 (4.s.f.)

    • 29.009 (5.s.f)

  • Zeros that come before all non-zero digits are not significant

    • 0.00079 (2.s.f.)

    • 0.48 (2.s.f.)

  • Trailing zeros in a whole number (no decimal point) are usually not significant, unless the context shows they were measured

    • 57,000 (2.s.f)

    • 640 (2.s.f)

  • Trailing zeros after the decimal point are significant

    • 6.890 (4.s.f)

    • 0.0500 (3.s.f)

• When rounding to a certain number of significant figures:

  • Identify the significant figures within the number using the rules above

  • Count from the first significant figure to the specified number

  • Use the next number as the ‘rounder decider’

  • If the decider is 5 or greater, increase the previous value by 1