What is a wave?
A periodic oscillation that transfers energy from one place to another.
What is a longitudinal wave? Give an example.
Oscillations are parallel to the direction of travel; e.g. sound waves.
What is a transverse wave? Give an example.
Oscillations are perpendicular to the direction of travel; e.g. ocean waves.
State the wave equation.
v = fλ
What did Hans Ørsted discover in 1820?
A current-carrying wire produces a magnetic field.
What did Michael Faraday show in the 1830s?
Changing magnetic fields produce electric fields.
What was James Clerk Maxwell’s contribution in 1861?
Developed Maxwell’s equations showing light is electromagnetic radiation.
What did Heinrich Hertz demonstrate in the 1880s?
The existence of radio waves, which behave like light.
Write the wave equation for light.
c = fλ where c = 3.00 × 10^8 ms^-1
How did Ole Rømer estimate the speed of light in the 1600s?
By observing the eclipses of Jupiter’s moon Io.
Who provided a closer estimate in 1727 using starlight?
James Bradley.
How did Hippolyte Fizeau measure the speed of light in 1849?
Using a toothed wheel and mirror 8 km away.
How did Léon Foucault refine Fizeau’s method?
By using a rotating mirror.
What value of the speed of light is used today?
c = 299,792,458 ms^-1
What is the wavelength range of visible light?
390–780 nm.
Which has greater penetrating power, short or long wavelength EMR?
Short wavelength EMR (e.g. X-rays, gamma rays).
Why can’t AM radio waves escape Earth’s atmosphere?
Their long wavelength means very low penetrating power.
