618941
| Pregunta | Respuesta |
| Describe examples of oscillations | - A mass on a string (bouncing) - A person bouncing on a trampoline - Someone walking backwards and forwards - A swing (swinging) - Air molecules as soundwave passes by - The molecules in any solid material |
| Define: Displacement | The distance of a particle from its undistributed position |
| Define: Amplitude | The maximum displacement of a particle from its equilibrium position |
| Define: Frequency | The number of waves/oscillations produced per second. |
| Define: Period | The time taken for one complete oscillation of a particle |
| Define: Phase difference | The phase difference between two particles along a wave is diffraction of a cycle by which one moves behind the other. |
| Define: Simple Harmonic Motion (SHM) | Motion where the acceleration of the particle is proportional to but in the opposite direction to the displacement of the particle. |
| Describe the interchange between kinetic energy and potential energy during SHM | If a mass is swinging on a pendulum, at the top of the swing it has the most potential energy, but the least KE. At the bottom of the swing the PE has been converted into KE and it has the greatest speed. |
| State what is meant by damping | It is the process by which energy is removed from an occilating system. Frequency does not change. The time for each cycle remains the same. |
| Describe examples of damped oscillations | - Child on a swing. Air resistance. - Soundwave. Absorption of vibrations (surroundings). - Waterwave. Wind forces and water resistance |
| Define: Light damping, heavier damping, critical damping | Light: Little resistance = little reduction. (spring in air) Heavier: More resistance =more reduction (spring in water) Critical: Resistance so great that the whole system returns to its equilibrium position w/o passing through it (spring in honey). |
| State what is meant by natural frequency of vibration and forced oscillations | Natural frequency: The frequency that the system oscillates naturally Forced oscillations: An oscillation (other than the natural frequency) that is brought about and maintained by the application of a force |
| Define: Resonance | An increase in amplitude that occurs when an oscillating system is forced to oscillate at its own natural frequency. |
| Describe examples of resonance where the effect is useful and where it should be avoided | Useful: Violin, microwave ovens, ultrasound Nuisance: Aircraft shattering windows,bridge collapse, vibrations in cars, |
| Describe a wave pulse and a continuous progressive (travelling) wave | A wave pulse involves just one oscillation. A continuous wave involves a succession of individual oscillations. |
| Does a travelling wave transfer energy? | Yes. Also, there is no net motion of the medium through which the wave travels. |
| Describe and give examples of transverse and of longitudal waves | Transverse: Waterwave, light. Goes up and down (direction of oscillation). Longitudal: Sound. Goes left to right. |
| Describe waves in two dimensions, including the concepts of wavefronts and of rays | Wave fronts:These are the movement of the wave pattern, i.e. when the curve is going up, or going down. The wave fronts highlight the parts of the waves which are moving together. Rays: highlight general direction of the wave and therefore the direction of the energy transfer. |
| Describe: Crest | The point at a wave with maximum positive displacement |
| Describe:Trough | The point on a wave with maximum negative displacement |
| Describe:Compression | The region where particles are closer together than they would be in equilibrium. |
| Describe: Rarefaction | When particles are further away than they would be in equilibrium. |
| Define: Wave speed | The distance travelled by the wave profile per unit time. |
| Define: intensity | Energy of a wave, more intense sound=loud, more intense light=brighter. |
| Electromagnetic spectrum (EMS) | Gamma rays: 10^-15m X-rays: 10^-15m Ultraviolet radiation: 10^-9m Visible radiation (light): 10^-7m Infrared radiation: 10^-5m Microwaves: 10^-2m Radiowaves:10m |
| Describe the reflection and transmission of waves at a boundary between two media (this includes sketching of incident, reflected and transmitted waves) | Reflection: In this case the law of reflection applies incident angle = reflected angle when measured from the normal ( an imaginary line at right angles to the surface). Refraction: In this case the wave is refracted towards the normal entering a slower medium and away from the normal entering faster medium. |
| State Snell's law | When light passes through different materials (for example from air to glass) the ratio of sines of the incidence (incoming) angle and the refraction (outgoing) angle does not change |
| Define: Diffraction | Diffraction is when the wave spreads out after passing through a narrow opening |
| Describe examples of diffraction | Water waves entering a harbor opening and spreading out. You can hear the TV from upstairs in your room if it is loud enough. |
| The principle of superposition | When two or more waves meet the total displacement at any point is the sum of the displacements that each individual wave would cause at that point. |
| What is meant by constructive and destructive interference? | Constructive: where the resultant wave is bigger than either of the two original. Destructive: The sum of two waves can be less than either wave, alone, and can even be zero (not in phase) |
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