Wave Properties 1.Describe the reﬂection and transmission of waves at aboundary between two media Usually, when a wave meets the boundary between two di erent media it ispartially reﬂected and partially trasmitted. As you can see from the diagram, there is a red line dividing the two‘mediums”. You should know that the Medium below is denser than themedium above. 2. State and apply Snell’s law Snell’s Law states that the ratio : V= Velocity The two sines divided by each other is also equal to “k”, which is a constantfor a given frequency.
3. Explain and discuss qualitatively the di raction of waves atapertures and obstacles When waves pass through apertures they tend to spread out. Waves alsospread around obstacles. This is called di raction. -The wavelength needs to of the same order of magnitude as the aperture fordi raction to be noticeable. -Di raction becomes important when the wavelength is large in comparison tosize of aperture.
4. Describe examples of di raction -Provides explanation of why we can hear something but cannot see it. If theWavelength= Aperture Length, a perfect di raction occurs, therefore thesound wave spreads perfectly, allowing people close by to hear the sound, butnot necessarily see the able. -If you look at a distant street light at night and then squint your eyes the lightspreads sideways—This is because of the di raction taking place around youreyelashes. 5. State the principle of superposition and explain what ismeant by constructive interference and by destructiveinterference When two waves of the same type meet, they interfere with each other, andwe can work out the resulting wave using the “Principle of Superposition”. Theoverall disturbance at any point and at any time where waves meet is thevector sum of the disturbances that would have been produced by each of theindividual wave. As you can see, the two waves below are added together like a vector toproduce the ﬁnal result at the top. When waves that have the same amplitude and frequency interfere with eachother, then the interference at a particular point can be either constructive ordestructive. Constructive
Destructive Interference 6. State and apply the conditions for constructive and fordestructive interference in terms of path di erence and phasedi erence. Constructive Interference takes place when the two waves are “in step” withone another—aka. In phase. Destructive Interference takes place when the waves are exactly “out ofstep”–they are said to be “out of phase” Interference can take place if there are two possible routes for a ray to travelfrom source to observer. If the path di erence between the two rays is a wholenumber of wavelengths, Constructive Interference will take place. Path Di erence: n x wavelength= constructive Path Di erence: (n+1/2) x wavelength= destructive n=0,1,2,3 7. Apply the principle of superposition to determine theresultant of two waves This is simply the vector sum of the waves that are in phase with each other.