SC Standards Covered

2. SC Standards Covered • Standard PS-7.5 Summarize the characteristics of the electromagnetic spectrum (including range of wavelengths, frequency, energy, and propagation without a medium). • Standard PS-7.7 Explain the Doppler effect conceptually in terms of the frequency of the waves and the pitch of the sound.

3. The Electromagnetic Spectrum • Electromagnetic waves – electric and magnetic waves released by a vibrating electric charge • Do not need a medium to travel through • All travel at 30, 000, 000 m/s • Travel through space in Photons that have no mass

4. Electromagnetic Spectrum • Electromagnetic spectrum – the entire range of frequencies of electromagnetic waves Low energy High energy Long wavelength short wavelength Low frequency high frequency

5. Radio Waves • Waves with a wavelength greater than 1m • Uses: • Radio signals • MRI • Studying objects in space

6. Microwaves • Waves with a wavelength from 1 m to 1 mm • Uses: • cellular telephones • Satellite signals • Heating / cooking food • RADAR • Doppler Radar

7. Infrared Waves • Waves with a wavelength between 1mm and 400 billionths of a meter • Feels like heat • Uses: • Remote controls • CD-ROMS • Infrared photography • Keep objects warm

8. Visible Light • Waves with wavelengths from 400 billionths of a meter to 750 billionths of a meter • Uses • Waves that we use to see

9. Ultraviolet Waves • Waves with wavelengths of 750 billionths to 10 billionths of a meter • The sun is an example, but most is blocked by the ozone layer • Enters into skin cells • Uses: • Causes our skin to make vitamin D • To kill bacteria • Causes some objects to fluoresce • To tan

10. X-Rays & Gamma Rays • Smallest wavelength electromagnetic waves • Travel through matter breaking molecular bonds • Uses: • X-ray imaging • Radiation therapy • Check for defects and cracks in metallic objects

12. The Doppler Effect • Doppler Effect – the change in frequency, pitch, due to a moving wave source

13. Using the Doppler Effect • Radar • Shoot radar waves towards a moving object and based on how the wavelengths are shifted, the velocity of the moving object can be determined

14. When an object is moving towards you the waves are compressed together, lowering the wavelength, increasing the frequency, which raises the pitch • Click here to see animation

15. When an object is moving away from you, the waves are spread apart more, raising the wavelength, decreasing the frequency, which lowers the pitch • Click here to see animation

16. Light Waves • Object must reflect light to be seen • When light strikes an object some colors of light are absorbed and some are reflected---we see the reflected colors • Lenses are used to redirect light waves - concave - convex

17. Convex • AKA: Converging lens • Thicker at the middle than at the ends • Corrects far-sightedness and for magnification • Bends light inward to a single focal point

18. Concave • AKA: Diverging lens • Concave lenses are thicker at the ends and bends all light outward • Used for the correction of near-sightedness

19. Light waves • Light waves can interfere constructively and destructively • The amplitude of a light wave is observed as brightness • Darker areas show destructive • Lighter areas show constructive • Sometimes light waves will interfere to produce a color pattern. When a color of light interfere destructively , we will not see that color. We only see the colors that are not interfered with.

20. Light Continued  • Light waves refract when they move from one medium to another • The light must hit at any other angle than perpendicular and change speed Light slows down as it enters the prism and bends down when it strikes at this angle When light exits, it speeds back up and bends down again

22. Get EOC book • Do pages 68-74 on notebook paper • You make work in pairs ONLY