1. WAVES: LIGHT moving Waves carry energy from one place to another

2. The NATURE of WAVES Waves – A wave is a disturbance that transfers energy. A medium – A substance which transmits a wave. Speed of waves – depends on the properties of the medium.

3. This drawing shows 1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

4. This drawing shows 1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

5. This drawing shows 1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

6. This drawing shows 1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

7. Light & the Electromagnetic Spectrum

8. LIGHT: What Is It? Light Energy Atoms As atoms absorb energy, electrons jump out to a higher energy level. Electrons release light when falling down to the lower energy level. Photons - bundles/packets of energy released when the electrons fall. Light: a stream of Photons

9. Electromagnetic Waves Speed in Vacuum 300,000 km/sec 186,000 mi/sec Speed in Other Materials Light is slower in Air, Water, Glass

10. Transverse Waves Energy is perpendicular to direction of motion Moving photon creates electric & magnetic field Light has BOTH Electric & Magnetic fields at right angles!

11. Electromagnetic Spectrum

12. Radio Waves Longest wavelength & lowest frequency. Size of a football field + Radio & T.V. broadcasting.

14. Electromagnetic Spectrum Microwaves About the size of a baseball Used in radar, cooking, pagers, cells

16. Electromagnetic Spectrum Infrared Rays Light rays with longer wavelength than red light. Longer IR is heat Cooking, Medicine, T.V. remote controls

18. Which is the same thing as heat? 1. Visible light 2. Infrared light 3. Radio waves 4. Ultraviolet radiation

19. This drawing shows 1. convection 2. transmitted energy 3. conduction 4. absorbed energy

20. This drawing shows 1. convection 2. transmitted energy 3. conduction 4. absorbed energy

21. LandSat satellite

22. Electromagnetic Spectrum Visible Spectrum – Light we can see Roy G. Biv – Acronym for Red, Orange, Yellow, Green, Blue, Indigo, & Violet. Largest to Smallest Wavelength.

23. Electromagnetic Spectrum Ultraviolet rays. EM waves slightly shorter than visible light Used in food processing & hospitals to kill germs’ cells Helps your body use vitamin D.

25. Electromagnetic Spectrum X-Rays are shorter than UV rays. Medicine – Bones absorb x-rays; soft tissue does not. Lead absorbs X-rays.

27. Electromagnetic Spectrum Gamma rays Shortest wavelength EM waves. They come from outer space. Uses: cancer treatment.

29. The Atmosphere absorbs wavelengths

30. LIGHT: Particles or Waves? Wave Model of Light Explains most properties of light Particle Theory of Light Photoelectric Effect – Photons of light produce free electrons

31. LIGHT: Refraction of Light Refraction – Bending of light due to a change in speed. Index of Refraction – Amount by which a material refracts light. Prism – Glass that bends light. Different frequencies are bent different amounts & light is broken out into different colors.

32. Refraction

33. LIGHT & Reflection Reflection – Bouncing back of light waves Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear & exact. Diffuse reflection – reflected light is scattered due to an irregular surface.

34. Color of Light Color of Objects White light is the presence of ALL the colors of the visible spectrum. Black objects absorb ALL the colors and no light is reflected back.

35. How You See Retina – Lens refracts light to converge on the retina. Nerves transmit the image Rods – Nerve cells in the retina. Very sensitive to light & dark Cones – Nerve cells help to see light/color

37. How You See Near Sighted – Eyeball is too long and image focuses in front of the retina Far Sighted – Eyeball is too short so image is focused behind the retina. © 2000 Microsoft Clip Gallery

38. LIGHT & USES: LASERS LASERS Acronym: Light Amplification by Stimulated Emission of Radiation Coherent Light – Waves are in phase so it is VERY powerful & VERY intense.

39. Summary Waves carry energy from one place to another The Electromagnetic Spectrum is an arrangement of 7 kinds of radiation, based on their wavelength Each kind of radiation has different wavelengths Each color of light has different wavelengths

40. Summary Radio waves, microwaves, infrared rays, light, ultraviolet light, x-rays and gamma rays are different wavelength bands in the spectrum of electromagnetic waves The speed of EM radiation in vacuum is approximately 186,000 miles/sec

41. The End… © 2000 Microsoft Clip Gallery