7. Wave Effects: Refraction Plastic Due to the plastic the water becomes shallower causing the waves to slow down. This effect is called refraction.
8. Wave Effects: Diffraction Diffraction is when the light bends around obstacles. Wider gaps produce less defraction.
9. Sound waves Sound waves are caused by vibration Sound waves consist of Longitudinal waves. - Compression passes Air pressure increases -Rarefaction passes Air pressure decreases
10. Sound Waves Sound waves need a medium to travel in. For instance the air. Sound waves can also be diffracted due to their long wavelength. They can be displayed on an oscilloscope. The sound enters via the microphone, a metal plate vibrates, these vibrations cause electrical oscillations producing a wave front. IT IS NOT A PICTURE OF THE SOUND WAVE BECAUSE SOUND WAVES ARE NOT TRANSVERSE
11. Speed of Sound Temperature of air: Sound travels faster through hot air. Does NOT depend on pressure: the pressure may change but the speed of the wave will remain the same The speed of sound is different through different materials. Ultrasound: sounds above the range of human hearing.
16. Total Internal Reflection Anything greater than the critical angle does not have a refracted ray. Which means that all the light is reflected thus leading to TOTAL internal reflection.
17. Lenses Convex Lens Concave Lens Convex lenses are used in projectors as they form large, inverted, real images on the screen
31. Electricity Rubbing materials does not MAKE charge, it only separates charges that are already there. Induced charge: this is the charge that ‘appear’ on an uncharged object because of the charged object nearby. Charge is measured in Coulombs.
33. Electricity When there are no ions in the air it is a good electrical insulator. When there are ions present in the air it is a good conductor Current is measured in amps.
34. Current Current remains the same at all points round a simple circuit. x Time Current Charge = Conventional Current flows from positive to negative. Electron flow is from negative to positive.
35. Potential Difference (Voltage) The highest potential difference is when it is not in a circuit and it not supplying current. This is also known as the Electromotive force. In a simple circuit, the sum of the PD’s across the components is equal to the PD across the battery.
36. Resistance PD (Voltage) V = = Resistance R I Current (A) Ohms Law The current is proportional to the PD.
37. How can resistance be increased? 1- Length : Doubling the length increases resistance 2- Cross-sectional area: halving the surface area. (thin wire is more resistance than a thick one) 3- Material 4- Temperature: resistance increases with temperature