1. Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine tomburbine@astro.umass.edu

2. Quiz on Thursday Magnetism Waves Light c = λ*f E = h*f Electromagnetic spctrum Doppler shift

3. Wave Something that vibrates in space and time Light acts as a wave Sound acts as a wave

5. Frequency The number of vibrations per unit time

6. Light Light is a form of energy

7. Light These are all forms of light –Gamma rays –X-rays –Ultraviolet light –Visible light –Infrared light –Radio waves

8. Light Can act as a particle Can also act as a wave

9. Particle aspect Particles called photons stream from the Sun and can be blocked by your body

10. Photons Light is quantized Comes in discrete packets called photons

11. Wave aspect

12. Thomas Young Experiment http://micro.magnet.fsu.edu/primer/java/interference/dou bleslit/http://micro.magnet.fsu.edu/primer/java/interference/dou bleslit/

13. Characteristics of waves velocity = wavelength x frequency Wavelength = distance Frequency = cycles per second = hertz 3 x 10 8 m/s

14. Speed of sound Speed of sound = 340 m / s

15. For light c = wavelength x frequency In vacuum, speed of light stays the same So if wavelength goes up Frequency does down f = frequency λ = wavelength c = λ x f

16. Calculations c = λ x f So if the wavelength is 1 x 10 -12 m 3 x 10 8 m/s = 1 x 10 -12 m * f f = 3 x 10 8 m/s/1 x 10 -12 m f = 3 x 10 20 s -1 = 3 x 10 20 Hz

17. Calculations c = λ x f So if the frequency is 1 x 10 15 Hz 3 x 10 8 m/s = λ * 1 x 10 15 Hz λ = 3 x 10 8 m/s/1 x 10 15 Hz λ = 3 x 10 -7 m

18. Energy of light Energy is directly proportional to the frequency E = h * f h = Planck’s constant = 6.626 x 10 -34 J/s since f = c/λ Energy is inversely proportional to the wavelength E = hc/λ

19. Higher the frequency, Higher the energy of the photon Higher the wavelength, Lower the energy of the photon

20. Calculations What is the energy of a radio wave with a frequency of 1 x 10 7 Hz? E = h * f h = Planck’s constant = 6.626 x 10 -34 J/s E = 6.626 x 10 -34 J/s * 1 x 10 7 E = 6.626 x 10 -27 J

21. Calculations What is the energy of a gamma ray photon with wavelength of 1 x 10 -15 m E = hc/λ h = Planck’s constant = 6.626 x 10 -34 J/s E = 6.626 x 10 -34 J/s * 3 x 10 8 m/s / 1 x 10 -15 m E = 1.99 x 10 -10 J

22. So why are some types of radiation dangerous? Higher the energy, the farther the photons can penetrate So gamma and X-rays can pass much more easily into your the body These high-energy photons can ionize atoms in cells Ionization means removes electrons from an atom

23. More dangerous

24. http://www.arpansa.gov.au/images/basics/emr.jpg

25. ROYGBIV Red – long wavelength Violet – short wavelength

26. Doppler Shift If a light or sound source moves towards you, the wavelength you measure (hear) from the source decreases –Frequency increases If a light or sound source moves away from you, the wavelength you measure (hear) from the source increases –Frequency decreases

27. http://www.youtube.com/watch?v=- t63xYSgmKE&feature=relatedhttp://www.youtube.com/watch?v=- t63xYSgmKE&feature=related

28. Doppler Shift http://www.psi.edu/~esquerdo/asp/shifts.jpg

30. http://www.youtube.com/watch?v=a3RfULw7aA Yhttp://www.youtube.com/watch?v=a3RfULw7aA Y

31. http://www.psi.edu/~esquerdo/asp/method.html Wavelength

32. Any Questions?