Understanding Waves: Types, Properties, and Phenomena
Transverse and Longitudinal Waves
Transverse Wave (e.g., Light): Vibrations are perpendicular to the direction of wave motion.
Longitudinal Wave (e.g., Sound): Vibrations are parallel to the direction of wave motion.
Key Wave Properties
- Wavelength: The distance between any two corresponding parts of the wave.
- Amplitude: The maximum distance the wave moves from the equilibrium position.
- Frequency: The number of waves per second.
- Period: The time taken for one complete wave to pass a point.
Wave Phenomena
Diffraction
Diffraction: The bending of a wave as it passes around the edge of a barrier. The wavelength remains the same.
Wave Interference
Wave Interference: Occurs when two waves meet while traveling along the same medium.
- Constructive Interference: Occurs when two waves meet and have a displacement in the same direction, superimposing to create a larger amplitude. Crest meets crest, or trough meets trough. This results in anti-nodal points with maximum amplitude (in phase).
- Destructive Interference: Occurs when two waves meet and have a displacement in the opposite direction, superimposing to cancel each other out. Crest meets trough. This results in nodal points with minimal or no amplitude (out of phase).
Diffraction Gratings
Factors influencing diffraction patterns:
- The slits are very thin, so the light diffracts through a wide angle.
- The slits are very closely spaced together, so the bright fringes are widely spaced.
- There are a larger number of slits, so the fringes are bright.
N is the number of slits per meter/centimeter, given by:
White light and diffraction gratings:
- White light contains many different frequencies (colors) of light.
- A diffraction grating produces a spectrum on each side of the central bright fringe.
- The greater the wavelength of the light, the greater the angle it is diffracted.
 |
Where:
- d is the slit separation.
- L is the distance to the screen.
- x is the distance from the central bright fringe.
| Antinodal Point | Nodal Point | x is directly proportional to wavelength: wavelength increases as spacing increases. |
 |  | x is directly proportional to L: as length increases, so does x. |
 |  | x is inversely proportional to d: as d increases, x decreases. |
Standing Waves
- Formed from the combination of two identical waves moving through each other in opposite directions.
- No net energy is transferred because each of the two waves carries energy in opposite directions.
- Energy is trapped in the wave and changes between kinetic and potential energy as the particles vibrate.
- The distance between two adjacent nodes is half the wavelength of the original wave.
How to change the frequency of a standing wave:
- Change the wavelength by changing the length of the string or pipe: shorter string = shorter wavelength = higher frequency.
- Change the tension: increase tension, then the speed increases, so the frequency is higher.
- Change the weight of the string: heavier string = lower frequency.
Beats
Beats: The rate at which the volume oscillates from high to low, heard when two sources produce sounds of slightly different frequencies.
The Doppler Effect
The Doppler Effect: The change in the apparent frequency of a sound caused by relative movement between the source of the sound and the listener.
Source moving towards you:
- Apparent upward shift in frequency.
- Pitch you hear is higher than emitted.
- Wavelength is shorter than emitted.
Source moving away from you:
- Apparent downward shift in frequency.
- Pitch you hear is lower than emitted.
- Wavelength is longer than emitted.