Presentation on theme: "One complete cycle (vibration) of a source will produce a wave (one crest, one trough). The frequency of the wave will be the same as the frequency of."— Presentation transcript:
One complete cycle (vibration) of a source will produce a wave (one crest, one trough). The frequency of the wave will be the same as the frequency of the source vibration. The time for the wave to travel a distance of one wavelength is the same as the time required for one vibration of the source (T). Universal Wave Equation: **Applies for all waves!
The speed of a wave does not depend on the frequency of the source, or the wavelength of the wave. The speed of a wave only depends on characteristics of the medium through which the wave propagates. http://www. physicsclassroom.com/Class/waves/u10l2d. html
Boundary Behaviour: From Investigation 6.2.1 it was observed that: Pulses reflected from a fixed end were inverted Pulses reflected from a free end were not inverted http://www.physicsclassroom.com/mmedia/waves/free.html http://www.physicsclassroom.com/mmedia/waves/fix.html
When a wave strikes the boundary between two media, partial reflection occurs. Two cases to consider: 1. Least dense More dense medium (faster to slower) http://www.physics classroom.com/mm edia/waves/ltm.html Transmitted PulseReflected Pulse Speeddecreasesunchanged Frequencyunchanged Wavelengthdecreasesunchanged Inversionnoneyes
2. More dense Less dense medium (slower to faster) Transmitted PulseReflected Pulse Speedincreasesunchanged Frequencyunchanged Wavelengthincreasesunchanged Inversionnone
Water waves behave in ways similar to waves in other media: Frequency – depends only on the source vibration (unchanging) Wavelength & Speed – vary according to the universal wave equation holding frequency constant Speed and wavelength are proportional e.g. As waves move from deep to shallow water the speed decreases. This causes the wavelength to decrease as frequency is unchanged (crests become closer).
Wavefront – leading edge of a wave (straight – line source or curved – point source) Wave ray – straight line drawn perpendicular to a wavefront to indicate the direction of propagation of a wave
Water waves approaching a barrier head on are reflected 180 degrees (opposite direction) Water waves approaching a barrier obliquely are reflected away at the same angle at which they approach. Angle of Angle of Incidence Reflection =
Refraction – the bending effect on a wave’s direction that occurs when a wave approaches a different medium at an angle. Refraction occurs because the change in media (deep to shallow or vice versa) causes a change in the speed of the waves, which proportionally causes a change in the wavelength of the wave. Refraction of water waves traveling from deep to shallow water. Notice the wavelength decreases causing the waves to refract or bend.
Diffraction – the bending effect on a wave’s direction that occurs when a wave passes through an opening or by an obstacle. Diffraction of waves passing through an opening in a barrier. Long waves lengths diffract (bend) more relative to shorter wavelengths.
Wave Interference – occurs when two or more waves act simultaneously on the same particles of a medium. Two ways in which waves can interfere: 1. Constructively 2. Destructively When waves encounter other waves in the same medium, they interfere with each other for an instant and then continue traveling unaffected.
Constructive Interference – occurs when waves having displacements in the same direction build each other up, resulting in a wave of larger amplitude than either of the two waves (temporarily).
Destructive Interference – occurs when waves having displacements in the opposite direction diminish each other, resulting in a wave of smaller amplitude than either of the two waves (temporarily).
Superposition principle – at any point the resulting amplitude of two waves is the algebraic sum of the displacements of the individual waves.
Before and after interference, waves traveling in the same medium do so as if they were traveling alone in the medium.
11U Physics Wave Motion Worksheet #1 1.Simple Pendulum a)What factor(s) affect the period of a simple pendulum? –Length of the pendulum –Force of gravity b)What is the equation for the period of a simple pendulum? c)Find the period of a pendulum of 3.00m. d)Rearrange the equation to solve for g:
11U Physics Wave Motion Worksheet #1 2.Transverse and Longitudinal Waves: a)Draw a diagram showing a tranvserse wave in a string, label a crest, trough, wavelength and amplitude. b) Draw a diagram showing a longitudinal wave in a string, label a compression, rarefaction, and wavelength. c) State the Universal wave equation relating speed and wavelength.
11U Physics Wave Motion Worksheet #1 3.Water Waves – The portions of water surface in which particles are all in the same phase of motion are called wave fronts. The direction of propagation of an advancing straight wave is perpendicular to the wave front. This is called rectilinear (straight-line) propagation. a)Copy the diagram on p. 216 showing waves reflected from a straight barrier. (Use wavelength of 1.0 cm) Waves approach barrier straight-on.Waves approach barrier at an angle.
11U Physics Wave Motion Worksheet #1 3. b) The speed of water waves in shallow water depends on the depth of the water and decreases as the water becomes less deep. What happens tot the wavelength and to the frequency if the speed changes as the waves move from deep to shallow water? See slide 19. c)Which equation applies for waves passing from one medium to another (e.g. deep to shallow) d) Draw a circular wavefront.See slide 20. e) What is a wave ray? See slide 20. f)Draw a diagram showing incident/reflected wave rays. See slide 21.
11U Physics Wave Motion Worksheet #1 3. g) What is the Law of Reflection? Law of Reflection – angle of incidence equals the angle of reflection. h)What happens when straight line waves are reflected by a parabolic reflector? A parabolic reflector (due to its shape) will focus all reflected rays at one point (focal point). This is the principle used in satellite dishes.
11U Physics Wave Motion Worksheet #1 4.Diffraction a)What is diffraction? See slide 23. b)For a fixed size of opening in a barrier, are shorter or longer wavelength waves diffracted more? See slide 23. c)For a fixed size of opening in a barrier, are high or low frequency waves diffracted more? Same amount.