1.  Wave  Characteris/cs  

Topic  Waves  

Overview  1.  Waves  -­‐–  Characteris/cs  (3  lessons)  

–  Transverse  vs.  longitudinal/Wave  characteris/cs  (ampl,  freq.  etc)  –  (1  lesson)  –  Wave  Equa/on/Proper/es  (Diffrac/on,  Reflec/on,  Refrac/on,  Interference  1-­‐D)  –  (2  lessons)  

2.  Light/Electromagne/c  Waves  –  (10  lessons)  –  EM  spectrum  –  (2  lessons)  –  Essay  (2  lessons)    –  Light  Basics  –  (1  lesson)  –  Reflec/on  in  Plane  mirrors  –  (2  lessons)    –  Refrac/on  –  (3  lessons)  

•  Dispersion  •  Snell’s  Law  •  Total  Internal  Reflec/on/Cri/cal  Angle  

–  Lenses  –  (2  lessons)  •  Basics  •  Thin  Lens  equa/on/Lens  maker  formula  •  Magnifica/on  •  Applica/on  

3.  Sound  –  5  lessons  –  Evidence  for  sound  as  a  wave  –  (1  lesson)  

•  Audacity    Ac/vity  –  Speed  of  Sound/Echoes/Refrac/on/Diffrac/on  –  (2  lessons)  –  Physics  of  Music/Human  Hearing/Ultrasound  –  (2  lessons)  

1.  Wave  Characteris/cs  

1) Amplitude – is the maximum displacement of particles from their resting position.

2) Wavelength (λ) – this is the distance between two corresponding points on the wave (e.g. two crests) and is measured in metres.

3) Frequency (f)– this is how many waves pass by a fixed point every second and is measured in Hertz (Hz)

Wave  Characteris/cs  4) Time period T: the time it takes one full wave to pass a fixed point.

𝑓= 1/𝑇   

Wave  speed  

v  =  λ  f  Deriva/on:        Units:        Example:    

Find  the  Wavelength  

•  You  listen  to  Kiss  100.  The  frequency  of  the  radio  sta/on  is  100MHz.  (1MHz  =  1,000,000Hz).  What  is  the  physical  dimension  of  this  wave,  i.e.  how  long  is  it?    

Answer  

•  λ=v/f=300,000,000/100,000,000=3m  

Longitudinal  and  Transverse  Waves  �  Longitudinal  waves:  the  direc/on  of  displacement  of  the  slinky/par/cles  is  parallel  to  the  direc/on  in  which  the  wave  travels.    

   � Transverse  waves:  the  direc/on  of  displacement  of  the  slinky/par/cles  is  perpendicular  to  the  direc/on  in  which  the  waves  travels.      

Longitudinal  and  Transverse  Waves  examples  

Longitudinal  waves:    �  sound,    �  primary  seismic  waves,    �  compression  waves  on  a  slinky.  

Tranverse  waves:    �  Electromagne/c  waves  (e.g.  light)    �  secondary  seismic  waves  and    �  waves  on  a  string  or  wire  (e.g.  violin,  guitar)  

Wave  proper/es:  reflec/on  

Law  of  reflec/on:    The  angle  of  incidence  θi  is  equal  to  the  angle  of  reflec/on  θr.      

Refrac/on:  examples  

•     

What  colour  do  you  see  on  the  board?    

•  Red  •  Yellow  

10/11/14

Wave  proper/es:  refrac/on  

Wave slows down and bends towards the normal due to

entering a more dense medium

Wave speeds up and bends away from the

normal due to entering a less dense medium

When  a  wave  crosses  a  boundary  between  two  media  at  an  angle  other  than  90°  it  will  change  its  direc/on  of  travel.  This  is  called  refrac/on.    

Water  wave:    

Ray  of  light  

glass  

air  

air  

Wave  proper/es:  diffrac/on  

Diffrac/on  has  the  strongest  effect  when  the  wavelength  λ  is  similar  to  width  of  the  gap.    

Wave  proper/es:  interference  

When  two  waves  meet  the  displacements  of  the  par/cles  add  up.  If  the  waves  are  in  phase,  then  construc.ve  interference  occurs.  If  they  are  fully  out  of  phase,  destruc.ve  interference  occurs.      

Wave  proper/es:  interference  -­‐  example