1. Waves and Optics Chapters 16-17, 24-26
Physics Notes
Waves and Optics
Chapters
16-17, 24-26

2. Comparing Types of Waves
Wave - the motion of a disturbance that transmits energy
Comparing Types of Waves
1. Mechanical vs Electromagnetic
Mechanical - requires a medium to transfer energy
ie. slinky, water, sound, earthquake
Electromagnetic - requires no medium
ie. radio, micro, IR, visual, UV, X, gamma

3. 3. Transverse vs Longitudinal
Transverse – Particles or disturbance vibrate perpendicularly to the direction of energy transfer
ie. light, slinky
Longitudinal - Particles vibrate parallel to the direction of the energy transfer (Pressure Wave)
compression vs rarefraction
ie. sound, slinky

4. Transverse Waves

5. Transverse and Longitudinal Waves

6. Aspects of all SHM (including waves)
Amplitude (A) - maximum displacement from equilibrium (m) Intensity or Energy
Period (T) - time to complete 1 cycle of motion (sec)
Frequency (f) - number of cycles per unit time (Hz)
T = 1 f = 1
f T

7. More Characteristics of Waves
Crest and Trough- the highest and lowest points from the equilibrium position
Wavelength (l) - The distance between two adjacent similar points of a periodic wave (m)
Node - Position on a standing wave that has no displacement
Antinode – Position on a standing wave that is displaced to its maximum displacement

9. Standing Wave – when two waves traveling in opposite directions interfere
The waves must have the same f, A, and l
Points of complete constructive and destructive interference

10. Standing Waves

11. In Phase – points on a wave in the same point in their cycle
Which points are in phase?
C and F
How many degrees out of phase are these 2 waves? 90

12. V = [F/ (m/L)] ½ The Speed of a Wave on a string or spring
Add Example Problem

13. V = d t V = f l = l T f = 1 The Speed of a Wave
The speed of sound in air is 331 m/s
The speed of light in a vacuum is 3.00 x 108 m/s = c
Add Example Problem

14. *Notes from “Activity: Waves and Springs”
What happens to a wave form when there is a disturbance in the medium through which it is traveling???
Standing Waves
Wave interactions
Interference: Constructive
Destructive

15. Constructive Interference

16. Destructive Interference

18. Reflection of a Pulse

19. Sound Sound waves are __________ and ___________.
Pitch - how high or low we perceive sound to be, depending on the frequency of the sound wave
The audible range for humans is 20 Hz to 20,000 Hz.
Ultrasonic waves: Medical applications, animal communication, others...
Speed of sound depends on the medium in which it is traveling in. Speed generally increases with:
denser phase
higher temperature

21. Sound does not travel in a linear wave as we sometimes model it
Sound does not travel in a linear wave as we sometimes model it. It really travels in 3D.
Wave fronts - the concentric spheres of compression radiating from the source of the sound

22. V – Velocity of Sound (331 m/s)
Doppler Effect - frequency shift that is the result of relative motion between the source of waves and an observer
moving towards f1 = f / (1 - Vs/V)
moving away f1 = f / (1 + Vs/V)
f = emitted frequency
f1 = perceived frequency
V – Velocity of Sound (331 m/s)
Vs – Relative velocity of the Source
Hear the Doppler Effect
Great Physlet
Click here to see the video of a plane breaking
the sound barrier
Know Red Shift and Blue Shift

23. Doppler Effect

24. Intensity - rate at which energy flows through a unit area perpendicular to the direction of wave motion
intensity = P = P
A 4pr2
Decibel Level (dB) - relative intensity of sound (logarithmic relationship)

25. Natural frequency - certain frequency at which an object vibrates
Resonance - a condition that exists when the frequency of a force applied to a system matches the natural frequency of vibration of the system.
Disastrous effects from earthquakes or winds

26. Harmonics
fundamental frequency - the lowest frequency of vibration of a standing wave
harmonic series - series of frequencies that includes the fundamental frequency and integral multiples of the fundamental frequency (overtones)
Standing wave on a vibrating string
Pipe open at both ends
Pipe closed at one end

27. Beat - interference of waves of slightly different frequencies traveling in the same direction, perceived as a variation in loudness
interference: constructive and destructive
f beat = (f1 - f2 ) or (f2 - f1 )
Create and Hear Beats:

28. Light waves are __________ and __________.
Electromagnetic Waves –
a transverse wave consisting
of oscillating electric
and magnetic fields
at right angles to
each other

29. Radio, Micro, IR, light, UV, X, Gamma Range of l and f

30. Light
Visible Spectrum (l = 700 nm to 400 nm)
700 nm = 700 x 10-9 m = 7.00 x 10-7 m
Again, a range of colors: ROY G BV

31. v = f l = d/t c = f l Wave speed
For light, (c = speed of light = 3.00 x 108 m/s)
c = f l
All electromagnetic waves move at the speed of light and behave with the characteristics of light, but they can not be detected by the eye

32. 3 x 108 m x 1 year x 365 days x 24 hours x 3600 s
Light Year – the distance that light travels in a year
d = V x t = 3 x 108 m/s x 1 year
now convert
3 x 108 m x 1 year x 365 days x 24 hours x 3600 s
s year day hour
d = 9.46 x 1015 m

33. Luminous –vs- Illuminated
Luminous Flux (P) - the rate at which visible light is emitted from a source.
Unit = lumen (lm) or Watt
Illuminance (E) - the rate at which light falls on a surface
Unit = lux (lx) = lm/m2 or Watt/m2 or candela
E = P = P (sphere)
A 4pr2
Luminous –vs- Illuminated
Luminous Intesity (l) – the luminuous flux that falls on an area of 1 m2
Unit – candela or candle power

34. Light Amplification by Simulated Emission of Radiation
LASER - a device that produces an intense, nearly parallel beam of coherent light
Light Amplification by Simulated Emission of Radiation
Applications:
Diffraction - the spreading of a wave into a region behind an obstruction
energy is dispersed
may result in areas of constructive and destructive interference
Spectral Emissions and Absorption

35. = d sin q Single Slit Diffraction Double Slit Diffraction
Maxima – Constructive Interference
d sin q = m l
Minima – Destructive Interference
d sin q = (m + ½) l
m = order of the maxima (0, 1, 2, 3…)
d = distance between slits
Single Slit Diffraction
= d sin q
d = width of slit

38. angle of incidence = angle of reflection
What happens when waves interact with matter?
Reflection - the turning back of waves at the surface of a substance
angle of incidence = angle of reflection
qi = qr
both angles are relative to the normal at the point of contact
virtual image - an image formed by light rays that only appear to intersect
flat mirror-

40. Mirrors
Convex/Concave
Virtual/Real
Upright/Inverted
Radius of Curvature and Focal Length
Object and Image Distance
Magnification

41. Mirrors
1 + 1 = 1
so si f
Magnification
M = h1 = - si
h so

42. Mirror Notes and Equations
* Given through “Activity: Concave and Convex Mirrors”
Convex/Concave
Virtual/Real
Upright/Inverted
Radius of Curvature and Focal Length
Object and Image Distance
Magnification
Great Physlet

43. Reflection: The color that we perceive an object to be is the color of the light which that object reflects

44. Light Amplification by Simulated Emission of Radiation
LASER - a device that produces an intense, nearly parallel beam of coherent light
Light Amplification by Simulated Emission of Radiation
Applications:

45. Polarization: The alignment of transverse waves in such a way that their vibrations are parallel to each other
-some crystals naturally polarize
-polymers
-double polarization
-applications: reflected glare is generally horizontal

47. Refraction: The bending of wave disturbance as it passes at an angle from one medium into another
different media result in different speeds of transmission
Index of Refraction (n):
-ratio of speeds of light
n = c v

48. n1 (sin q1) = n2(sin q2) n2 = V1 = l1 n1 V2 l2
The degree of refraction is determined by:
Snell’s Law
n1 (sin q1) = n2(sin q2)
know bending towards or away
As a wave travels from a medium to another velocity and wavelength change, but frequency does not.
n2 = V1 = l1
n V l2

53. Dispersion – when white light separates into the spectrum of colors - results because different wavelengths travel at different speeds and refract differently

55. Total Internal Reflection - the complete reflection of light at the boundary of two transparent media; this effect occurs when the angle of incidence exceeds the critical angle
Critical angle
sin qc = nr ni
only when ni > nr

56. converging lenses vs diverging lenses
Lens - a transparent object that refracts light rays, causing them to converge or diverge to create an image
converging lenses vs diverging lenses
focal point (f) for a lens is the image distance for an object at an infinite distance
f is: + for converging, - for diverging
Ray Diagrams: 3 reference rays
Is the Image:
Real or Virtual
Upright or Inverted
Enlarged or Smaller

57. For lenses, the distance equation is similar to that of mirrors
1 + 1 = 1
so si f
Magnification
M = h1 = - si
h so
Lenses:
the eye
glasses - combination of lenses

58. Lens Power
P =1 f
Unit: diopter (D)