The Four Forces of Nature

1. The Four Forces of Nature • Gravity • Holds the Solar System together • Electromagnetic • Holds atoms together • Strong Nuclear (Nuclear) • Holds the nucleus together • Weak Nuclear • Radioactive decay • There is energy associated with each of these forces

2. Waves  v • Waves always involve two types of energy that convert back and forth • The wavelength  is the distance from one wave to the next • The frequency f is how often it repeats per second • The velocity v is how fast it moves • If you multiply the distance it goes in one cycle () times the number of cycles in a second (f), you will get how far it goes in a second (v) v = f

3. Electromagnetic Waves • Electric and Magnetic fields • Light is a type of electromagnetic wave • Speed isgiven by c c = lf f frequency l wavelength c speed of light c =3  108 m/s Q. 14: Wavelengths of Radio Waves

4. The Electromagnetic Spectrum • Visible Light is only small part of spectrum • 0.4 – 0.7m

5. The Electromagnetic Spectrum

6. The Electromagnetic Spectrum f Increasing  Increasing These too Not these Know these, in order • Different types of waves are classified by their frequency (or wavelength) ROY G. BIV Radio Waves Microwaves Infrared Visible Ultraviolet X-rays Gamma Rays Red Orange Yellow Green Blue Violet Vermillion Saffron Chartreuse Turquoise Indigo Q. 15: Speed of Different Colors

7. Light and Color Red Orange Yellow Green Blue Violet • Some colors can be made with just one wavelength of light • Other colors are made with different combinations of wavelengths • Black is the result of no light • White is a combination of all colors of light • If you put white light through a spectrometer, you get allthecolorsoftherainbow

8. The Doppler Effect

9. The Doppler Effect • Light is shifted towards longer wavelength when objects are moving away from you • Called “red shift” • Light is shifted towards shorter wavelength when objects are moving towards you • Called “blue shift”

10. The Doppler Effect • Waves from a moving source are affected by motion of source • Motion towards and away from you are all that matter c = 3108 m/s rest natural wavelength shift observed wavelength vrad velocity away from you c speed of light

11. The Doppler Effect A laser makes light with a wavelength of 0.500 m. It is put aboard a rocket and detected at a wavelength of 0.499 m. How fast is the rocket moving? A) 6  105 m/s away from us B) 6  105 m/s towards us C) 1.5  1014 m/s away from us D) 1.5  1014 m/s towards us c = 3108 m/s

12. Light and Quantum Mechanics f • Light energy comes in packets called photons • Amount of energy depends on frequency E = h f Q. 16: Which Has More Power? h = Planck’s Constant

13. Atoms + – – – + + Electromagnetic Forces • There are electric and magnetic forces • Electric forces affect anything with electric charge • Electric charges come in two types, positive and negative • Like charges repel, unlike charges attract • Electric forces are much stronger than gravity

14. nucleus electrons Atoms – the Solar System model • Atom has two pieces: • The nucleus is heavy and positivelycharged. Its charge tells you whatkind of atom you have • Electrons are light andhave charge -1 • In ordinary circumstances,the total charge is zero • The electrons orbit thenucleus, like the planets orbit the Sun +1 Hydrogen +2 Helium +26 Iron Q. 17: The Exploding Professor?