VIDEO SUMMARIES: WAVES
DIFFRACTION*
What#you#need#to#know:#
v
1.  ###
= fλ
v=#Velocity#(msG1)#
f #=#Frequency#–#Hertz#(Hz)#
λ =#Wavelength#(m)#
2.  Diffrac+on#is#the#bending#of#waves#as#they#pass#
obstacles#in#their#path#
3.  Waves#diffract#when#the#wave#length#(λ)#is#
similar#to#the#gap#size#
SUPERPOSITION
*
What-you-need-to-know:1.  Superposi+on-is-when-two-or-more-waves-overlap-andthe-result-is-the-sum-of-the-individual-waves2.  Phase-refers-to-the-posi+on-of-the-wave3.  Construc+ve-interference-is-where-waves-overlap-inphase-producing-a-bigger-wave4.  Destruc+ve-interference-is-where-waves-overlap-out-ofphase-cancelling-each-other-out---
WWW.LEARNCOACH.CO.NZ
VIDEO SUMMARIES: WAVES
INTERFERENCE+
What$you$need$to$know:$
1.  A$source$of$light$can$diffract$through$two$slits$
causing$an$interference+pa-ern++
2.  The$waves$that$have$passed$through$the$slits$
overlap$to$produce$lines$of$construc9ve$
interference$(an9nodal$lines)$and$destruc9ve$
interference$(nodal$lines)$
3.  This$is$shown$by$areas$of$high$intensity$
(construc9ve$interference)$and$low$intensity$
(destruc9ve$interference)$
WAVE%REFRACTION%–%PART%1%
What-you-need-to-know:1.  Refrac)on:-the-bending-of-a-wave-as-it-passes-fromone-medium-to-another2.  When-a-wave-moves-from-a-less-to-a-more-densemedium-it-bends-TOWARDS-the-normal3.  When-a-wave-enters-a-more-dense-medium-v-–-decreases,-λ-–-decreases,-f-–-constant.4.  n-is-the-refrac)ve-index-and-measures-the-op)caldensity-of-a-material-
WWW.LEARNCOACH.CO.NZ
VIDEO SUMMARIES: WAVES
WAVE%REFRACTION%–%PART%2%
What)you)need)to)know:)
1.  Reflected)waves:)The)angle)of)incidence)equals)the)
angle)of)reflec:on)(θi = θr)
2.  Shallow)water)is)like)high)n
Deep)water)is)like)low)n)
3.  Remember)three)S’s:)))Shallow,)Short,)Slow)
4.  Ra:o:))
n1 v2 λ2
= =
n2 v1 λ1
RAY$REFRACTION$–$PART$1$
What(you(need(to(know:(
1.  Waves(refract(when(passing(from(one(medium(to(another(
•  They(bend(towards(the(normal(when(entering(a(MORE(DENSE(
material((
•  They(bend(away(from(the(normal(when(entering(a(LESS(DENSE(
material.(
2.  ((n1 sin θ1
3. 
= n2 sin θ 2
n1 =(RefracGve(Index(1(
θ1 (=(Angle(of(incidence(
n2 =(RefracGve(Index(2(
θ2 (=(Angle(of(RefracGon(
θi and(θr(are(measured(against(the(normal(
WWW.LEARNCOACH.CO.NZ
θi
θr
VIDEO SUMMARIES: WAVES
1.  Total(internal(reflec/on(acts(like(a(perfect(mirror(where,(the(angle(of(
incidence(equals(the(angle(of(reflec/on((θi = θref)(
2.  Total(internal(reflec/on(occurs(when:(
•  The(angle(of(incidence(is(greater(than(the(cri/cal(angle((θi > θc)(
•  Light(is(aiming(to(travel(from(a(more(dense(to(a(less(dense((((
((((((medium((
3.  When(calcula/ng(the(cri/cal(angle,(the(refracted(ray((θr)(is(ALWAYS(90°(
when(light(is(aiming(to(travel(from(a(more(dense(to(a(less(dense(medium((
!f!is!the!focal!length!!
!f!is!half!the!centre!of!curvature!(c)
!
di hi 1 1 1 !di!is!the!distance!from%the%lens!to!the!image
!
m =
= +
=
!do!is!the!distance!from%the%lens!to!the!object!
f di d o
d o ho
!hi!is!the!height!of!the!image!
!ho!is!the!height!of!the!object!
!m!is!the!magnifica8on!
do
di
ho
image!
c! object!
c! h
f!
f!
i
RAY$REFRACTION$–$PART$2$
What(you(need(to(know:(
INTRODUCTION)TO)RAY)DIAGRAMS)
What!you!need!to!know:!
WWW.LEARNCOACH.CO.NZ
VIDEO SUMMARIES: WAVES
CONVEX'LENS'DIAGRAMS'
What"you"need"to"know:"
•  To"Draw"
1.  Straight"through"centre"
2.  In"parallel,"then"through"the"focal"point"
3.  Dot"back"if"necessary"
•  Proper?es/Characteris?cs:"
!  Enlarged"vs."Diminished"
!  Upright"vs."Inverted"
!  Real"vs."Virtual"
•  If"object"is"outside"f:"
(real,"inverted,"diminished/enlarged)"
•  If"object"is"inside"f:"
(virtual,"enlarged,"upright)"
f"
f"
f"
f"
CONCAVE'LENS'DIAGRAMS'
What#you#need#to#know:#
•  To#Draw:#
1. Straight#through#centre#
2. In#parallel,#then#out#from#the#focal#point#(dot#out)#
3. Dot#back#if#necessary#
•  The#image#is:#
Enlarged#vs.#Diminished#
Upright#vs.#Inverted#
f#
f#
Real#vs.#Virtual#
x
x
x
WWW.LEARNCOACH.CO.NZ
VIDEO SUMMARIES: WAVES
CONCAVE'MIRROR'DIAGRAMS'
What"you"need"to"know:"
•  To"Draw:"
1.  Into"centre,"out"on"same"angle"
2.  In"parallel,"back"through"focal"point"
3.  Dot"back"to"get"image"
•  If"object"is"outside"f:"
(real,"inverted,"diminished/enlarged)" image"
•  If"object"is"inside"f:"
c"object"
(virtual,"enlarged,"upright)"
f"
CONVEX'MIRROR'DIAGRAMS'
What#you#need#to#know:#
•  To#Draw:#
1.  Into#centre,#out#on#same#angle#
2.  In#parallel,#out#(dot#back#from#focal#point)#
3.  Dot#back#outgoing#rays#
•  Image#is#always:#
x
x
Enlarged#vs.#Diminished#
Upright#vs.#Inverted#
Real#vs.#Virtual#
x
object#
WWW.LEARNCOACH.CO.NZ
image#
f#