1. Key points Formulae Physics IGCSE Revision(Part 2) Simple Easy By: Momina

2. Sound Waves-Describing them Amplitude Wavelength

3. Transverse Waves The oscillations are at right angles to the direction of the wave. For example light waves.

4. Longitudinal Wave ( Rarefactions) It consists of compressions and rarefactions. Oscillations are in direction of travel. For example: Sound waves.

5. The Wave Equation x x wavelength Frequency V f = Speed = = Lambda

6. Wave Effects: Reflection The waves are reflected from the surface at the same angle they hit it.

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.

13. Electronic tape measure (Works like an echo-sounder)

15. Law of reflection i˚=r˚ i, r and normal lie on the same plane.

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

19. Larger

20. Virtual

22. Inverted

23. The same size

25. Inverted

26. Larger

28. Inverted

29. Smaller

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.

32. Electricity* Electrostatic precipitators: are fitted into chimneys in order to reduce pollution

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

39. One bulb removed the other still works

40. Total current = Sum of the currents in the branches.

42. One bulb removed, the other one goes out.

43. Current through each component is the same

45. Power Work done = Power Time take

46. Power x x Voltage V I P Current Power = =

47. Power x x 2 Resistance V I P Current Power = = 2

48. Electrical Energy Equation x x x I x Current Energy Transformed = = E t PD V Time

50. Electrons and Electronics

51. Atoms and Radioactivity