4.5+WAVE+PROPERTIES

Back to IB PHYSICS > OSCILLATIONS AND WAVES =4.5 WAVE PROPERTIES= 4.1 KINEMATICS OF SHM 4.2 ENERGY CHANGES DURING SHM 4.3 FORCED OSCILLATION AND RESONANCE 4.4 WAVE CHARACTERISTICS
 * 1 Measure || 2 Mech || 3 Therm || 4 Waves || 5 Electric || 6 Fields || 7 Atomic || 8 EPCC || 9 MIF || 10 Therm AHL || 11 Wave Phen || 12 EMI || 13 QNP || 14 Digital || OPT || PRAC || REVISE ||

ACTIVITY - RIPPLE TANK SIMULATION - see the screenshots examples.

Describe the reflection and transmission of waves at a boundary between two media. This should include the sketching of incident, reflected and transmitted waves. REFRACTION: Change of direction at a boundary due to different wavespeed SNELL’S LAW: For two particular media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

State and apply Snell’s law. Students should be able to define refractive index in terms of the ratio of the speeds of the wave in the two media and also in terms of the angles of incidence and refraction.

**(use a pencil, protractor, ruler and eraser and be prepared to re-draw)** Draw the boundary between two media in which the speed of a wave in the first one is less than the speed in the second one. Sketch an incident ray and then wavefronts perpendicular to it. Construct the refracted ray and wavefronts. Measure the respective angles to calculate the refractive index and then the ratio fo the wavelengths. Are they related? Why? Extension: Draw the situation of critical angle of incidence for these waves.
 * DRAWING ACTIVITY 1 - REFRACTION **



Explain and discuss qualitatively the diffraction of waves at apertures and obstacles.

DIFFRACTION: The spreading of waves when they pass through an opening or round an obstacle.



The effect of wavelength compared to aperture or obstacle dimensions should be discussed. Describe examples of diffraction.



State the principle of superposition and explain what is meant by constructive interference and by destructive interference.

Try out interference using these two simulations:

[|Online ripple tank] [|PHET simulation] (if ISL student, find it in Course/US/WeatherellS/Phet Simulations/Waves)

SUPERPOSITION: When two waves pass the same point at the same time, their displacements are added together to calculate the resultant displacement. INTERFERENCE: Superposition of coherent sources resulting in an interference pattern.

CONSTRUCTIVE/ DESTRUCTIVE: Interference in which the resultant is reinforced/ cancelled.





State and apply the conditions for constructive and for destructive interference in terms of path difference and phase difference.

COHERENT: Sources of waves with a constant phase difference are coherent.

Apply the principle of superposition to determine the resultant of two waves.

**DRAWING ACTIVITY 2 - SUPERPOSITION** **(use a pencil, ruler and eraser and be prepared to re-draw)** Across a sheet of graph paper, draw one period of a sinusoidal displacement-distance graph. Below this, draw another wave with half of the wavelength and the same amplitude (two periods). On a third graph below the other two, choose at least eight intervals and plot the resultant of their displacements at each point. Extension: Draw another wave (maybe half the wavelength again, but you may choose) on axes below the resultant graph, and add it to the resultant.

**DRAWING ACTIVITY 3 - INTERFERENCE** **(use a pencil, compasses, ruler and eraser and be prepared to re-draw)** Draw two point sources and then construct concentric wavefronts from each one. Plot the lines of constructive and destructive interference and indicate their path and phase differences. Extension: Draw the situation if the sources are out of phase by π rads?