Waves

You will be able to

• Use v = fλ and f = 1/T, reading the wavelength from a displacement–distance graph and the period from a displacement–time graph.
• Calculate the phase difference between two points on a progressive wave as (Δx / λ) × 360°, in degrees and in radians.
• State that the intensity of a wave is proportional to the square of its amplitude.

You will be able to

• Explain why a source moving relative to a stationary observer changes the observed frequency and wavelength.
• Calculate the observed frequency with fₒ = fₛv / (v ± vₛ) for a source approaching or receding from a stationary observer.
• Calculate the wavelength in front of a moving source as (v − vₛ) / fₛ.

You will be able to

• Explain that a polarising filter transmits only the component of the oscillations along its transmission axis, so unpolarised light loses half its intensity.
• Use Malus's law, I = I₀ cos²θ, to calculate the intensity transmitted by an analyser.
• Determine I₀ from the gradient of a graph of I against cos²θ.