EJC Physics H211 Waves 2023 1. Notes (full)

Ocean waves exhibit both transverse and longitudinal behaviour. It is observed that particles near the water surface move in a vertical circular motion without significant net displacements in their average positions as a wave propagates. This wave motion “flattens” out as the ocean wave reaches shallower waters, resulting in more of a forward/backward ebbing motion near coasts. This phenomenon also partially explains why tsunamis are devastating: as a tsunami reaches shallower water, its speed of propagation is forced to slow down, its horizontal wavelength is forced to decrease and the kinetic energy is converted to gravitational potential energy – the wave height increases dramatically before smashing onto coastal areas. Content • Progressive waves • Transverse and longitudinal waves • Polarisation • Determination of frequency and wavelength of sound waves Learning Objectives: Candidates should be able to: (a) show an understanding of and use the terms displacement, amplitude, period, frequency, phase difference, wavelength and speed (b) deduce, from the definitions of speed, frequency and wavelength, the equation 𝑣 = 𝑓𝜆 (c) recall and use the equation 𝑣 = 𝑓𝜆 (d) show an understanding that energy is transferred due to a progressive wave (e) recall and use the relationship, intensity ∝ (amplitude)2 (f) show an understanding of and apply the concept that a wave from a point source and travelling without loss of energy obeys an inverse square law to solve problems (g) analyse and interpret graphical representations of transverse and longitudinal waves (h) show an understanding that polarisation is a phenomenon associated with transverse waves (i) recall and use Malus’ law ( intensity ∝ cos2 θ) to calculate the amplitude and intensity of a plane polarised electromagnetic wave after transmission through a polarising filter (j) determine the frequency of sound using a calibrated oscilloscope (k) determine the wavelength of sound using stationary waves (* to be done in H212 Superposition)

We think of waves as a “bulk phenomenon” – it happens on a larger scale and are made up of adjacent smaller units (such as water molecules, gas molecules, rope segments) individually exhibiting oscillations. Waves can result in energy (but not matter) being moved from one point to another OR energy can also be confined to a region in space without transfer. In this topic, w e will focus on the former : progressive waves. In our A-Levels journey we will encounter 3 main types of waves: Mechanical waves e.g. water waves, sound waves and seismic waves (earthquakes). They obey Newton’s laws of motion, and can only exist within a material medium (correspondingly liquid water, air, rock). Electromagnetic waves do not need a material medium to exist. They travel through vacuum at a speed of 8110 30 m s0c. −= . Visible light ranges from 400 nm to 700 nm. Take note of the order of magnitude of E