1. Wave Model of Radiation Revision

2. Waves Waves are disturbances that transfer energy in the direction of the wave without transferring matter. Waves are disturbances that transfer energy in the direction of the wave without transferring matter. The frequency is the number of waves per second. The frequency is the number of waves per second. Wavelength is the distance between the same point on 2 adjacent disturbances. Wavelength is the distance between the same point on 2 adjacent disturbances. Amplitude is the distance between the crest or trough and the undisturbed position. Amplitude is the distance between the crest or trough and the undisturbed position. Speed = frequency x wavelength. Speed = frequency x wavelength.

3. Longitudinal and Transverse Waves Longitudinal Wave Longitudinal Wave –Particles vibrate in same direction that the wave moves. Transverse Wave Transverse Wave –Particles vibrate at 90 degrees to the direction that the wave moves.

4. Wave Diagrams Waves in water can be shown using diagrams. Waves in water can be shown using diagrams.

5. Reflection Ripples can also bounce off a barrier, and they can be made to change direction.

6. Refraction When waves enter a different depth they change speed – and direction. When waves enter a different depth they change speed – and direction.

7. Light as a wave Because light acts in a similar way to water it is considered a wave also. Because light acts in a similar way to water it is considered a wave also. Light can be reflected and refracted also. Light can be reflected and refracted also. Diagrams for light waves are different. Diagrams for light waves are different.

8. The Electromagnetic Spectrum All types of EM waves travel at the same speed. All types of EM waves travel at the same speed. EM waves can travel through a vacuum unlike sound waves. EM waves can travel through a vacuum unlike sound waves. Different colours have different wavelengths and frequencies. Different colours have different wavelengths and frequencies. Different wavelengths have different uses due to their differences in reflection, absorption and transmission by different materials. Different wavelengths have different uses due to their differences in reflection, absorption and transmission by different materials.

9. The EM Spectrum

10. Uses of EM Radiation Gamma and X rays penetrate human flesh and are used for medical purposes. Gamma and X rays penetrate human flesh and are used for medical purposes. Microwaves penetrate the atmosphere and are used for mobiles and other devices that use satellites. Microwaves penetrate the atmosphere and are used for mobiles and other devices that use satellites. Satellite dishes and microwave ovens are made of metal because they reflect microwaves. Satellite dishes and microwave ovens are made of metal because they reflect microwaves. Radiowaves do not penetrate the atmosphere as well but can be reflected off the ionosphere over long distances. Radiowaves do not penetrate the atmosphere as well but can be reflected off the ionosphere over long distances.

11. Amplitude and Frequency Modulation Waves can carry information by varying in amplitude or frequency. Waves can carry information by varying in amplitude or frequency. Because the signal various the same way as the information, it is called analogue. Because the signal various the same way as the information, it is called analogue. When the radio waves meet a metal aerial they produce electrical waves which enter the receiver. When the radio waves meet a metal aerial they produce electrical waves which enter the receiver. The receiver reproduces the original signal from the pattern of variation. The receiver reproduces the original signal from the pattern of variation.

12. AM and FM Modulation

13. Digital Signals Signals can be carried by IR or light waves through optical fibres. Signals can be carried by IR or light waves through optical fibres. Other information can be transmitted digitally. Other information can be transmitted digitally. Sound is converted to a digital signal made from 0s and 1s. Sound is converted to a digital signal made from 0s and 1s. The coded information controls the bursts of waves (pulses). The coded information controls the bursts of waves (pulses). 0 = no pulse, 1= pulse. 0 = no pulse, 1= pulse. When the waves are received the pulses are decoded to produce the original information. When the waves are received the pulses are decoded to produce the original information.

14. Digital Quality Radio signals become weaker as they travel and pick up random signals called noise. Radio signals become weaker as they travel and pick up random signals called noise. Amplification also amplifies the noise so the quality deteriorates. Amplification also amplifies the noise so the quality deteriorates. Digital signals are not as affected by noise as they are either on or off. Digital signals are not as affected by noise as they are either on or off. Digital signals therefore maintain their quality. Digital signals therefore maintain their quality.

15. Digital Radio