8.1 Stationary waves:
- The principle of superposition states that when two or more waves meet, the resulting displacement is the algebraic sum of the individual displacements.
- Stationary waves are formed by the superposition of two progressive waves with the same frequency and amplitude traveling in opposite directions.
- Nodes are points of zero displacement in a stationary wave, while antinodes are points of maximum displacement.
- Wavelength can be determined by measuring the distance between consecutive nodes or antinodes.
8.2 Diffraction:
- Diffraction refers to the bending and spreading of waves as they encounter an obstacle or pass through an aperture.
- Diffraction experiments demonstrate the qualitative effect of the gap width relative to the wavelength of the wave.
- For example, water waves in a ripple tank can exhibit diffraction patterns when they encounter a barrier with an aperture.
8.3 Interference:
- Interference occurs when two or more waves combine to form regions of constructive and destructive interference.
- Interference experiments demonstrate the behavior of waves interfering with each other, such as water waves, sound waves, light waves, and microwaves.
- Interference fringes, which are regions of constructive and destructive interference, can be observed under certain conditions.
- The conditions for observing two-source interference fringes include coherent sources, a constant phase difference, and a narrow source width.
8.4 The diffraction grating:
- The diffraction grating is a device that consists of a large number of equally spaced parallel slits or lines.
- The grating equation, d sin θ = nλ, relates the wavelength (λ) of light to the separation between the grating lines (d), the order of the diffraction (n), and the angle of diffraction (θ).
- A diffraction grating can be used to determine the wavelength of light by measuring the angle of diffraction.