Wave motion lecture notes and Tutorial

1 Lecturer: Mr Eugene Tan Email: tan.sweehong@dhs.sg Content • Progressive waves • Transverse and longitudinal waves • Polarisation • Determination of frequency and wavelength Learning Outcomes Candidates should be able to: (a) show an understanding and use the terms displacement, amplitude, phase difference, period, frequency, 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) analyse and interpret graphical representations of transverse and longitudinal waves. (g) show an understanding that polarisation is a phenomenon associated with transverse waves. (h) determine the frequency of sound using a calibrated c.r.o. (i) determine the wavelength of sound using stationary waves. 10.1 Progressive Waves A progressive wave transfers energy from one point to another by means of vibrations or oscillations within the waves. All waves involve a disturbance from an equilibrium position (i.e. an oscillation), and (for progressive waves,) the disturbance travels from one region of space to another. However, the particles do not move along with the disturbance. 10.2 Transverse and Longitudinal Waves Progressive Waves Transverse Waves Longitudinal Waves Electromagnetic Waves Mechanical Waves Mechanical Waves H1 / H2 PHYSICS (2013) TOPIC 10: WAVE MOTION

2 Transverse wave: Transverse wave is a wave in which the oscillation of the particles in the wave is perpendicular to the direction of transfer of energy of the wave. (E.g.: electromagnetic waves) Longitudinal wave: Longitudinal wave is a wave in which the oscillation of the particles in the wave is along the direction of transfer of energy of the wave. (E.g.: sound waves) Mechanical wave: A wave that requires a medium for its transmission. (E.g.: sound waves and water waves) Electromagnetic wave: Wave consisting of oscillating electric and magnetic fields that are at right angles to each other and to the direction of transfer of energy of wave. It does not require a medium for transmission. It can travel through a vacuum at the speed of light, i.e. 3 × 10 8 m s-1. (E.g.: radio waves, visible light, X-rays and microwaves) Electromagnetic Spectrum Type of Radiation Range of wavelength Range of Frequency Radio Waves 6 cm to 300 km (1 x 103 to 5 x 109) Hz Microwaves 10-3 m to 10-1 m (109 to 3 x 1011) Hz Infrared Radiation 7.8 x 10-7 m to 0.5 x 10-3 m (6 x 1011 to 4 x 1014) Hz Light (Visible Spectrum) 3.8 x 10-7 m to 7.8 x 10-7 m (4 x 1014 to 8 x 1014) Hz Ultraviolet Radiation 6 x 10-10 m to 3.8 x 10-7 m (8 x 1014 to 5 x 1017) Hz X-Rays 10-12 m to 10-9 m From 3 x 1020 Hz Gamma Rays 10-14 m