1. 24/06/2016 OCR Additional Science The Wave Model of Radiation W Richards A slideshow that covers the entire OCR 21 st Century 2006 Syllabus “Wave Model of Radiation” Module

2. 24/06/2016 Some definitions… 1) Amplitude – this is “how high” the wave is: 2) Wavelength ( ) – this is the distance between two corresponding points on the wave and is measured in metres: 3) Frequency – this is how many waves pass by every second and is measured in Hertz (Hz)

3. 24/06/2016 Transverse vs. longitudinal waves Transverse waves are when the displacement is at right angles to the direction of the wave (e.g. light and other electromagnetic waves)… Longitudinal waves are when the displacement is parallel to the direction of the wave (e.g. sound waves)… Displacement Direction Displacement

4. 24/06/2016 The Wave Equation The wave equation relates the speed of the wave to its frequency and wavelength: Wave speed (v) = frequency (f) x wavelength ( ) in m/s in Hz in m V f

5. 24/06/2016 1)A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? 2)A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? 3)The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 4)Purple light has a wavelength of around 6x10 -7 m and a frequency of 5x10 14 Hz. What is the speed of purple light? Some example wave equation questions 0.2m 0.5m 0.6m/s 3x10 8 m/s

6. 24/06/2016Reflection Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror Angle of incidence = Angle of reflection

7. 24/06/2016 Using mirrors Two examples: 1) A periscope 2) A car headlight

8. 24/06/2016 Refraction through a glass block: Wave slows down and bends towards the normal due to entering a more dense medium Wave speeds up and bends away from the normal due to entering a less dense medium Wave slows down but is not bent, due to entering along the normal

9. 24/06/2016

10. Refraction Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______. Words – speed up, water, air, bent, medium

11. 24/06/2016 Finding the Critical Angle… 1) Ray gets refracted 4) Ray gets internally reflected 3) Ray still gets refracted (just!) 2) Ray still gets refracted THE CRITICAL ANGLE

12. 24/06/2016 Wave behaviour 1) Reflection 4) Diffraction3) Refraction 2) Refraction

13. 24/06/2016Diffraction More diffraction if the size of the gap is similar to the wavelength More diffraction if wavelength is increased (or frequency decreased)

14. 24/06/2016 Sound can also be diffracted… The explosion can’t be seen over the hill, but it can be heard. We know sound travels as waves because sound can be refracted, reflected (echo) and diffracted.

15. 24/06/2016 Diffraction depends on frequency… A high frequency (short wavelength) wave doesn’t get diffracted much – the house won’t be able to receive it…

16. 24/06/2016 Diffraction depends on frequency… A low frequency (long wavelength) wave will get diffracted more, so the house can receive it…

17. 24/06/2016Interference Interference is seen when two waves of the same type cross:

18. 24/06/2016 Constructive and Destructive Interference

19. 24/06/2016 Interference Patterns from 2 slits Intensity Distance Constructive interference Destructive interference

20. 24/06/2016 The Visible Spectrum The spectrum can be seen when white light is refracted: RED LIGHT is refracted THE LEAST PURPLE LIGHT is refracted THE MOST

21. 24/06/2016 The electromagnetic spectrum Gamma rays X-raysUltra violetVisible light Infra redMicrowavesRadio/TV Visible light is just one part of the Electromagnetic Spectrum, a family of waves that all travel at the speed of light as transverse waves: The amount of energy these waves carry depends on the amount of energy carried by the _______ (very small particles) that make them up. Sound is not part of the EM spectrum because it travels as a _________ wave, which causes it to travel much _________ and be unable to travel through empty space like ______ can. Words – photons, light, long, short, longitudinal, slower High frequency, _____ wavelength Low frequency, _____ (high) wavelength γ

22. 24/06/2016 The Electromagnetic Spectrum Type of radiationUsesDangers Gamma rays X rays Ultra violet Visible light Infra red Microwaves TV/radio Treating cancer, sterilisation Medical Sun beds Seeing things Remote controls, heat transfer Satellites, phones Communications Cell mutation Skin cancer None (unless you look at the sun) Sunburn Very few

23. 24/06/2016 Transmitting information Sounds can be transmitted long distances by converting them into electrical signals first: Radio waves can also be used as “carrier waves”: Signal____ wave______ waveTransmitter Wave is demodulated back into a ____ Words – signal, frequency, modulated, carrier, sound, amplified A microphone converts ______ waves into electrical signals with the same amplitude and ________. These waves are then transmitted through cables where they are regularly _________ to reduce signal loss.

24. 24/06/2016 Frequency vs Amplitude Modulation 1) FM: 2) AM: Carrier Signal Carrier Signal Output

25. 24/06/2016 Analogue vs. Digital Analogue signals (like talking or music) continually vary in amplitude and/or frequency + - 1 0 Digital signals, however, are either off or on, and the information is sent in a series of pulses There are two main advantages of digital: 1)More information can be sent down the same cable 2)Better quality, because a digital signal can be amplified without amplifying the extra noise:

26. 24/06/2016 This slideshow has been made freely available on the TES Resources website. More Science PowerPoints like this can be found at the website www.educationusingpowerpoint.com. This site contains slideshows that cover the AQA, EdExcel, OCR Gateway and OCR 21st Century courses, including the 2011 units, and A Level Physics and KS3 material.www.educationusingpowerpoint.com Some slideshows are free, others require a small subscription fee to be taken out (currently only £50 for a year). Further details can be found at Education Using PowerPoint.Education Using PowerPoint