Physical Science / Unit 9: Waves, Sound and Light
9.2 Wave Properties and the Wave Equation
Notes
- Frequency (f): number of waves per second, in hertz (Hz). Period (T): time for one wave, $\displaystyle T = \frac{1}{f}$.
- Wavelength ($\lambda$): distance between repeating points.
- Wave speed: $v = f\lambda$.
- Example: $f = 5$ Hz and $\lambda = 2$ m gives $v = 10$ m/s.
- Higher amplitude means more energy. Wave speed depends on the medium, not on frequency.
Practice
A wave has a frequency of 4 Hz and a wavelength of 3 m. What is its speed?
$v = f\lambda = 4 \times 3 = 12$ m/s.
A wave has a speed of 20 m/s and a wavelength of 5 m. What is its frequency?
$\displaystyle f = \frac{v}{\lambda} = \frac{20}{5} = 4$.
A wave has a frequency of 4 Hz. What is its period?
$\displaystyle T = \frac{1}{4} = 0.25$ s.
Ready for more? Take the Unit 9 test.