DHS 14 Superposition (Notes & Tutorial)

Dunman High School (Senior High Physics) 1 Topic 14 – Superposition Content • Principle of superposition • Stationary waves • Diffraction • Two-source interference • Single slit and multiple slit diffraction Learning Outcomes Candidates should be able to: (a) explain and use the principle of superposition in simple applications (b) show an understanding of the terms interference, coherence, phase difference and path difference (c) show an understanding of experiments which demonstrate stationary waves using microwaves, stretched strings and air columns (d) explain the formation of a stationary wave using a graphical method, and identify nodes and antinodes (e) explain the meaning of the term diffraction (f) show an understanding of experiments which demonstrate diffraction including the diffraction of water waves in a ripple tank with both a wide gap and a narrow gap (g) show an understanding of experiments which demonstrate two-source interference using water waves, sound waves, light waves and microwaves (h) show an understanding of the conditions required for two-source interference fringes to be observed (i) recall and solve problems using the equation D ax=λ for double-slit interference (j) recall and use the equation b λθ =sin to locate the position of the first minima for single slit diffraction (k) recall and use the Rayleigh criterion b λθ ≈ for the resolving power of a single aperture (l) recall and use the equation d sinθ = nλ to locate the positions of the principal maxima produced by a diffraction grating (m) describe the use of a diffraction grating to determine the wavelength of light (the structure and use of a spectrometer are not required).

Dunman High School (Senior High Physics) 2 1 PRINCIPLE OF SUPERPOSITION In the previous topic, we only considered a single wave. Many interesting wave phenomena in nature are impossible to describe with a single progressive wave. In this topic, we will examine what happens when two (or more) waves pass through the same region of space at the same time. We see that after crossing each other, the waves travel as if nothing had happened and retain their original shape. Hence, pulses and waves pass through each other unaffected. When the waves meet each other, they add up vectorially to give the resultant wave. This combination of two (or more) waves to form a resultant wave follows the Principle of Superposition. Note: The two waves must be of the same type (sound, electromagnetic, etc). The Principle of Superposition states that when two or more waves of the same type meet at a point at the same time, the displacement of the resultant wave is the vector sum of the displacements of the individual waves at that point at that time. (a) explain and use the principle of superposition in simple applications. waves are some (e) The waves are receding from each other