EM Spectrum Calculations

Background

• Constant:   v = speed of light (3 x 10⁸ m/s)
• Variable:   λ=wavelength (m)
• Variable:   f = frequency (Hz)
• Formula:   λ = v ÷ f
• Example:   λ = 300,000,000 m/s ÷ 1,110,000 Hz = 270 m

Examples

1. Find wavelength when f = 3,000 Hz.     λ= v/f     λ = 3×10⁸ / 3000 = 100,000m or 100 km
2. Find wavelength when f = 300 MHz     λ= v/f     λ = 3×10⁸ / 300×10⁶ = 1m
3. Find the frequency when λ=3 cm     f = v/λ     f = 3X10⁸ / 3×10^-2 = 1×10¹⁰ Hz or 10 GHz
4. Find the frequency when λ=390 nm     f = v/λ     f = 3X10⁸ / 390×10^-9 = 7.7×10¹⁴ Hz or 770 THz

SI prefixes. Derived from Wikipedia

Prefix	Symbol	10n	Decimal	Short scale
exa	E	1018	1000000000000000000	Quintillion
peta	P	1015	1000000000000000	Quadrillion
tera	T	1012	1000000000000	Trillion
giga	G	109	1000000000	Billion
mega	M	106	1000000	Million
kilo	k	103	1000	Thousand
		100	1	One
centi	c	10-2	0.01	Hundredth
milli	m	10-3	0.001	Thousandth
micro	µ	10-6	0.000001	Millionth
nano	n	10-9	0.000000001	Billionth
pico	p	10-12	0.000000000001	Trillionth
femto	f	10-15	0.000000000000001	Quadrillionth
atto	a	10-18	0.000000000000000001	Quintillionth