yr9 - light and reflection
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- 1. Dr Pusey www.puseyscience.com Q: Are light waves longitudinal or transverse?
- 2. Light waves are electromagnetic waves that can travel through a vacuum.
- 3. Light Energy Light is a form of energy and can be changed from one form into another. For example in solar panels For example in plants Light energy Electrical energy Light energy Chemical energy
- 4. Different light frequencies produce different colour. The range of colours that we can see are known as the visible spectrum. Outside of the visible spectrum, we cannot see the electromagnetic waves. Higher frequency = Higher Energy!!
- 5. The Electromagnetic Spectrum https://en.wikipedia.org/wiki/Electromagnetic_spectrum
- 6. Ones you need to know Radio Waves Very long wavelength Walky Talkies Radio (Even digital) Television Infra-red Frequency is just below the colour red Associated with HEAT The warm part of sunlight
- 7. Ones you need to know Visible Waves Different colours are different frequencies within a small range White light is a combination of all visible frequencies! Ultra-Violet (UV) Frequency is just above the colour violet Associated with skin burns Can cause other types of damage (cancers)
- 8. Ones you need to know Microwaves Short wavelength PlayStation controller Bluetooth X-rays - Very short wavelength Can pass through soft human tissue (good for looking at bones) More risk of causing damage to humans Gamma-rays Super short wavelength Travels through nearly everything High risk of causing damage to humans (if it is absorbed!)
- 9. Quick Quiz Sort the following in their order of wavelength (shortest to longest) Radio Waves Microwaves Gamma Rays X Rays Visible Light Ultra-Violet Infra-Red
- 10. Quick Quiz Now, sort the following in their order of their Energy, (lowest to highest) Radio Waves Microwaves Gamma Rays X Rays Visible Light Ultra-Violet Infra-Red
- 11. The Electromagnetic Spectrum https://en.wikipedia.org/wiki/Electromagnetic_spectrum
- 12. How do we see things? An object that gives out light = luminous Light travels in a straight line from the object into your eyes. E.g. a light bulb
- 13. How do we see things? An object that does not give out light = non-luminous Light hits the rock and some of it is reflected into your eyes. E.g. a rock
- 14. Reflection There are 2 types of reflectors Regular reflectors these produce regular reflection Diffuse reflectors these produce diffuse reflection
- 15. Regular Reflectors Surface that is extremely smooth and shiny (E.g. A mirror) Light rays bounce off (reflect) in an orderly way.
- 16. Diffuse Reflectors Most surfaces around us are not super smooth, even if they might look it. A rough surface will cause light to be reflected imperfectly, in all different directions. Diffuse reflection occurs from these rough surfaces and no clear image is formed Many surfaces appear smooth but are rough compared with the surface of a mirror.
- 17. Reflectors What type of reflection are these diagrams showing? Give two examples of surfaces which show that type of reflection.
- 18. Law of Reflection: The angle of incidence is equal to the angle of reflection https://en.wikipedia.org/wiki/Reflection_%28physics%29 Incident Ray Reflected Ray Angle of Incidence Angle of Reflection Normal (to the surface) Fit the above terms to the diagram!
- 19. Law of Reflection: The angle of incidence is equal to the angle of reflection https://en.wikipedia.org/wiki/Reflection_%28physics%29 Incident Ray Reflected Ray Angle of Incidence Angle of Reflection Normal (to the surface)
- 20. Angle of Incidence (i) Angle of Reflection (r) 30 50 80 65 Reflection Quiz
- 21. Convex & Concave Mirrors Concave Dug out Like a Cave Can magnify things useful for make-up mirrors! Can focus light Torches & Telescopes Convex Bulges out Makes things appear smaller Security mirrors objects in mirror are closer than they appear www.physicsclassroom.com
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