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

Waves 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 v 

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

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

The Electromagnetic Spectrum

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

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 all the colors of the rainbow

The Doppler Effect

The Doppler Effect Called “red shift” Called “blue shift” 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”

The Doppler Effect c = 3108 m/s rest natural wavelength 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

The Doppler Effect c = 3108 m/s 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

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

Electromagnetic Forces 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 + – – +

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