1. Option G – Electromagnetic waves

2. Lesson 1 • Outline the nature of electromagnetic (EM) waves. • Describe the different regions of the electromagnetic spectrum. • Describe what is meant by the dispersion of EM waves. • Describe the dispersion of EM waves in terms of the dependence of refractive index on wavelength.

3. Nature of electromagnetic waves

4. Nature of electromagnetic waves • An oscillating electric charge produces varying electric and magnetic fields. • Electromagnetic waves are transverse waves and all have the same speed in a vacuum.

5. Electromagnetic spectrum λ ≈ 700 - 420 nm λ ≈ 10-4 - 10-6 m λ ≈ 10-7 - 10-8 m λ ≈ 10-9 - 10-11 m λ ≈ 10-2 - 10-3 m λ ≈ 10-1 - 103 m λ ≈ 10-12 - 10-14 m

6. Source of electromagnetic waves? • You have 15 minutes to take notes from pages 600 and 601 about how different EM waves are produced. http://phet.colorado.edu/sims/radio-waves/radio-waves_en.jar

7. Sources of EM radiation

8. Dispersion Let’s make rainbows!

9. A reminder - Snell’s law speed in substance 1 sinθ1 speed in substance 2 sinθ2 =

10. A reminder - Snell’s law In the case of light only, we usually define a quantity called the index of refraction for a given medium as n = c cm where c is the speed of light in a vacuum and cm is the speed of light in the medium c vacuum cm

11. Dispersion • This occurs because the index of refraction of the glass changes with wavelength. The index of refraction is slightly smaller for red light than it is for blue light, so the red light gets bent less.

12. Dispersion

13. Just one question! Page 605 Question 3