Curriculum+objectives

=Assessment Statements=

**4.2.3. Solve problems, both graphically and by calculation, involving energy changes during SHM. (AK)** --See number 24 on page 213 **4.3.1. State what is meant by damping. (AK)** --Damping refers to oscillations that take place in the presence outside forces (ie. the oscillations will eventually stop and the energy of the system will be given off as thermal energy). The degree of damping affects the reaction of the system. **4.3.2. Describe examples of damped oscillations. (AK)** --Damped oscillations include under-damping, critical damping, and over-damping. Under-damping refers to oscillations taking place with a frequency that decreases gradually until the amplitude approaches zero and oscillations stop. Critical damping refers to situations in which the amount of damping is large enough that the system returns to its equilibrium as fast as possible without performing oscillations. Over-damping refers to systems in which the degree of damping is so great that it returns to equilibrium without oscillations. It is similar to critical damping, but is //much// slower. **4.3.3. State what is meant by natural frequency of vibration and forced oscillations. (AK)** --Natural frequency of vibration refers to a system that takes place with no outside forces. Forced oscillations take place when an external force is applied on a system that is free to oscillate. The frequency is assumed to vary periodically. **4.3.4. Describe graphically the variation with forced frequency of the amplitude of vibration of an object close to its natural frequency of vibration. (AK)** --In the case of forced oscillations, a more closely applied force’s frequency is the natural frequency (and the oscillations become larger). Amplitude starts large, but gradually decreases due to the interference of outside forces. A graph will show the changes in the amplitude of oscillations over time. **4.3.5. State what is meant by resonance. (AK)** --The state in which the frequency of the externally applied periodic force equals the natural frequency of the system is called resonance. As a result, oscillations have larger amplitudes. **4.3.6. Describe examples of resonance where the effect is useful and where it should be avoided. (AK)** --Resonance should be avoided in cases such as the construction of airplane wings and buildings. However, it is useful in cases such as a quartz oscillator, which sends out resonant frequencies in electronics. **4.4.1. Describe a wave pulse and a continuous progressive (traveling) wave. (AK)** --Wave pulses occur when only one wave is sent at a time. The wave travels, passing energy from the start to the finish. Continuous waves are sent persistently one after the other, and the waves become frequent and consistent. A transverse or longitudinal wave is sometimes referred to as a traveling wave and these waves transfer energy away from a source by a wave pattern that moves through space. A //transverse wave// is a wave in which the oscillations are perpendicular to the direction of the transfer of energy. Examples are waves on a spring, surface waves of a pond, and any wave on the electromagnetic spectrum. A //longitudinal wave// is a wave in which the oscillations are in the same direction and parallel to the transfer of energy. Examples are sound waves and earthquakes and waves along a stretched spring. Waves in higher dimensions must satisfy the Principle of Superposition which governs how waves interact: whenever two or more waves pass through each other, the resulting disturbance at a given point in the medium may be found by adding the individual displacements that each wave would have caused. This law causes the wave front, all points affected by a wave, and the rays to change. A //crest// and a //trough// are parts of a transverse wave. A //crest// is the peak of a wave and is the maximum point of a wave's cycle and a //trough// is the minimum point of a cycle. A //compression// and a //rarefaction// are parts of a longitudinal wave. A //compression// is an area of high pressure and a //rarefaction// is an area of low pressure. //displacement//: the distance in a given direction from a fixed origin. It is a vector quantity that is measure in meters(m) //amplitude//: the maximum displacement of a wave. The square of the amplitude is proportional to the energy that is carried by the wave. It is represented in equations by "A". //frequency//: the number of full waves emitted per unit time. It is measure is Hertz or s^-1 //period//: the time that a wave takes to complete a full cycle. It is measured in seconds and represented by "T" //wavelength:// the distance between two points measured from one point on a wave to the same point on a consecutive cycle of the same wave, for example: crest to crest or trough to trough. It is measure in meters (m). //wave speed:// the speed at which a wave travels. (wave speed= frequency*wavelength) //intensity:// the average amount of energy transported by a wave in the direction of a wave propagation, per unit area per unit time. //wave speed= wavelength *frequency// Because electromagnetic waves do not require a medium to travel, all electromagnetic waves travel at the same speed in free space. The wavelengths of the principal radiations in the electromagnetic spectrum ascend in the following order: Gamma rays, X-rays, Ultra Violet, visible light, infrared, microwaves, radio waves.
 * 4.4.2 State that progressive (traveling) waves transfer energy.** (ER)
 * 4.4.3 Describe and give examples of transverse and longitudinal waves.** (ER)
 * 4.4.4 Describe waves in two dimensions, including the concept of wave fronts and of rays.** (ER)
 * 4.4.5 Describe the terms crest, trough, compression and rarefaction.** (ER)
 * 4.4.6 Define the terms displacement, amplitude, frequency, period, wavelength, wave speed, and intensity.** (ER)
 * 4.4.7 Draw an explain displacement-time graphs and displacement-position graphs for transverse and for longitudinal waves.** (ER)
 * 4.4.8 Derive and apply the relationship between wave speed and wavelength and frequency.** (ER)
 * Example 1: Find the frequency of a sound wave of wavelength 14 m.
 * v = 343 m/s and x = 14 m
 * 343 m/s = f * 14 m
 * //f= 24.5 Hz//
 * Example 2: Find the wavelength of a light wave of frequency 50 Hz
 * v = 3e8 m/s and f = 50 Hz
 * 3e8 m/s = 50 Hz * x
 * //x= 6e6 m//
 * 4.4.9 State that all electromagnetic waves travel with the same speed in free space, and recall the orders of magnitude of the wavelength of the principal radiations in the electromagnetic spectrum.** (ER)

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