Summary
Progressive waves are waves that transfer energy through a medium without transferring matter. They can be described by their properties such as phase, speed, frequency, and wavelength.
- Phase Difference — describes the relative positions of points within two waves of the same frequency. Example: When the crests of two waves align, they are "in phase" with a phase difference of 0 degrees.
- Cathode-Ray Oscilloscope (CRO) — a device used to visualize and analyze electrical waveforms. Example: A.C. current appears as a transverse wave on the CRO screen.
- Wave Equation — relates the speed, frequency, and wavelength of a wave. Example: v = fλ, where v is speed, f is frequency, and λ is wavelength.
- Wave Intensity — the energy passing through a unit area per unit time in a wave. Example: Intensity increases by a factor of 4 if amplitude or frequency is doubled.
- Spherical Waves — waves that propagate equally in all directions from a point source. Example: Intensity decreases with distance according to the inverse square law.
Exam Tips
Key Definitions to Remember
- Phase difference: the relative positions of points within two waves of the same frequency.
- Cathode-Ray Oscilloscope (CRO): a device for visualizing electrical waveforms.
- Wave Equation: v = fλ, relating speed, frequency, and wavelength.
- Wave Intensity: energy passing through a unit area per unit time.
Common Confusions
- Confusing phase difference with amplitude.
- Misinterpreting the CRO display as a direct representation of wave speed.
Typical Exam Questions
- What is the phase difference between two waves in phase? Answer: 0 degrees or 0 radians.
- How does a CRO display an A.C. current? Answer: As a transverse wave on the screen.
- What happens to wave speed if frequency is doubled and wavelength is halved? Answer: The wave speed remains the same.
What Examiners Usually Test
- Understanding of the wave equation and its components.
- Ability to interpret CRO readings and relate them to wave properties.
- Application of the inverse square law to wave intensity.