Welcome to PH 103 Dr. Cecilia Vogel Lecture 1

Class structure  Syllabus  You don’t want me to read it to you – so read it on your own!  Web page helios.augustana.edu/~cv/103helios.augustana.edu/~cv/103  print lectures before class  see in-class work after class  announcements, etc  Office  office hours in Hanson 120  my office is Hanson 121B  Course goals – “facts” are only a small fraction  WebAssign and Quizdom  Clarify: WebAssign homework is 10% of your grade (not pre-flights, which are also on WebAssign)  5% from pre-flight or in-class work or exam  If I’m grading it, it better be justified!  exception multiple choice

Quizdom Intro Press and hold “menu” to turn on Session ID: User ID: your student ID (or try a number 1-12 if you are not registered) To input, press the “send” key (double arrow) If this does not work, press “menu” and then use the arrows to find and change session or user ID manually

Light  Electromagnetic wave  oscillating electric and magnetic fields  means the field is sometimes big, sometimes small  E and B are abstract “fields”  -- not moving matter!  not wiggly path! =purple arrow along x-axis =path of light

Wave properties  wave moves at speed v   wavelength = distance between repeats  period = time between repeats  frequency = # oscillations per second f =v f (speed is c=3X10 8 m/s only in vacuum) T

How fast?  Frequency of wave  how fast is it oscillating?  depends on the thing that’s creating the oscillations  Speed of wave  how fast is it getting from point A to point B?  depends on the properties of the thing the wave is traveling through

MEMORIZE EM SPECTRUM  Visible:  Longer:  Shorter: = nm Infrared, microwave, radio UV, X-rays, gamma violet thru red

Speed of light  Speed of light is c=3X10 8 m/s, only in vacuum  Speed in other materials  is slower than vacuum  index of refraction, n  tells how much slower  in material, v=c/n  n=1 vacuum, n= air,  n=1.33 water, n=2.42 diamond

Material and Wavelength  Speed in other materials  is slower than vacuum  If light passes from vacuum to material  frequency is unchanged  but speed changes – what happens to   so wavelength decreases when speed decreases  in material,  v=c/n  =  /n