Physics : Prefixes and Uncertanties

Physics

Unit prefixes

Prefix name         Prefix abbreviation         Multiplier         Example

Tera             T                x10^12            0.000000000123T

Giga            G                x10^9            0.000000123G

Mega            M                x10^6            0.000123M

Kilo            K                x10^3            0.123K

Milo            m                x10^-3            123000m

Micro            µ                x10^-6            123000000µ

Nano            n                x10^-9            123000000000n

Pico             p                x10^-12        123000000000000p

• all the waves in the electromagnetic spectrum travel at a speed v=3.0 x10^8m/s

Wave            Frequency/Hz                Wavelength/Hz

        x10^power         with prefix        x10^power        with prefix

Infra red    1.5x10^14        150THz        2x10^-6        2µm

Ultra violet    1.5x10^15        1.5PHz        2x10^-7        0.2µm

vhf radio    1.0x10^8        100MHz        3            3m

x-rays        500x10^15        500PHz        6x10^-10        0.6nm

Visible light    4x10^14        400THz        7.5x10^-7        750nm

Uncertainty

• % uncertainty = (uncertainty / mean value) x 100
• the largest % is the most important
• when quantities are multiplied or divided, their percentage uncertainties are added
• accuracy indicates proximity to the correct answer
• When significant figures are used as an implicit way of indicating uncertainty, the last digit is considered uncertain.
• e.g. a result reported as 1.23 implies a minimum uncertainty of ±0.01