1. Waves and Lenses Pg

2. What is a WAVE
Wave: disturbance that travels through a medium (water, air, ground…)
Transports energy
It does NOT transport matter
Ripples are the result of a disturbance that spreads across the surface of the water
Picture a duck sitting in waves, the duck rises and falls but never moves Fig 4.2

3. Wave Characteristics
Propagates (spreads) in two ways: transverse and longitudinal
Transverse: its medium moves perpendicular to its motion
Fig 4.3
Wave moves from left to right, but medium moves up and down

4. Wave Vocab Highest point of wave: Crest Lowest point of wave: Trough
Transverse waves are made up of Crests and Troughs

5. Longitudinal Wave Medium moves parallel to the motion of the medium
When a longitudinal wave propagates through a medium, its particles move closer together and then farther apart
BUT always parallel to the direction of the wave’s motion
Compression: region where particles are close together
Rarefaction: region where particles are farther apart Fig 4.5 and 4.6

6. Amplitude
Amplitude (A) of a wave: Depends on the energy transmitted by a wave
The greater the energy transmitted, the greater the amplitude
(when you make a rope make waves, the higher the waves the more energy you must put in)
A: maximum distance travelled by a particle in the medium compared to its position at equilibrium
Frequency of a wave connects with the Pitch of a sound

7. Amplitude cont.
Transverse waves Amplitude: max. height of crest or max. depth of trough, from the position at equilibrium Fig 4.8
Longitudinal waves Amplitude: harder to measure. Depends on density of compression
The denser the region of Compression , the greater the Amplitude
Fig 4.9
Amplitude= Loudness of the sound

8. Wavelength ‘Lambda’ (λ) Is the length of a wave’s complete cycle
Transverse wavelength: distance between 2 consecutive crests or troughs
Longitudinal wavelength: length of 1 compression and 1 rarefaction
Fig 4.10 and 4.11 (copy in notes)

9. Frequency Frequency: number of cycles per unit of time
Measured in Hertz (Hz)
If a wave has a frequency of 1Hz, it completes one full cycle in one second
Speed= frequency x wavelength

10. Types of Waves 2 types of waves:
Mechanical
Electromagnetic
Mechanical wave: a wave that requires a medium (solid, liquid or gas) in order to propagate (spread out)
Ex: water is the medium for water waves, air is medium for sound waves, ground is medium for seismic waves during earthquake

11. Types of Waves cont.
Did you know that there is no sound in space….but our movies would be boring without this, so movie makers ignore this fact to make it more interesting for the viewer!!
Electromagnetic wave: is a wave that can travel in both vacuum and a medium
Ex: light waves (transverse waves) that move just as easily in a vacuum as a medium – Sun rays reach us through interstellar space and the atmosphere
Electromagnetic waves carry energy from point to another
Form of energy is radiant waves

12. Types of waves cont.
Electromagnetic waves ex: radio waves, light waves, ultraviolet waves, X-rays…

13. Pg. 98-99 Create a table in your notes using these pages Title
Description
1 example you choose
1 example related to health care

14. Sound Waves Sound: longitudinal mechanical wave
Produced by vibration of an object
Transmitted to the object’s environment
Ex: chair falls to floor, its impact causes particles in floor to vibrate, these disturbances are passed on to the surrounding medium (ex: air) the wave produced transmits sound energy

15. The Decibel Scale
Sound can be soft like a whisper or loud like a scream
Volume depends on intensity or energy is it transmitting
The greater the energy the greater the sound
Less energy = less amplitude = less sound
Intensity of sound is measured in Decibels (dB)

16. Decibel (dB)
Not an exact scale, relative to perception by the human ear
Decibels are measured in 10s, so when something is increased by 10 dB, it becomes 10 times louder
Sound measuring 40dB is 100 times louder than a 20dB sound
Decibels are not cumulative (two separate 50dB do not make 100 dB)

17. Dangerous Decibel levels
Fig 4.20
Prolonged exposure to sounds louder than 100 dB can cause long-term hearing damage
Starting at 120 dB pain and immediate hearing loss can ensue (ear protection needed)

18. Light Waves pg. 106
Light is an electromagnetic wave that is visible to the human eye
Ex: light bulb, sun, fire
Light waves travel in straight lines AKA light rays
Light waves can be reflected or refracted when they strike an object

19. Reflection
Reflection: rebounding of light that occurs when a light ray hits a different medium and ‘bounces back’ to the original medium
Ex light rays passing through air and rebounding off of a mirror
If we can see an object it is because reflection brings light to our eyes
Fig 4.26 copy this diagram into your books and label the lines

20. Reflection cont.
Incident ray: ray that contacts the surface of an object
Reflected ray: ray that rebounds
Normal: is a line perpendicular to the surface at the point of reflection
Angle of incidence: angle formed by the incident ray and the normal
Angle of reflection: angle formed by the reflected ray and the normal

21. Reflection cont. Reflection:
Diffuse reflection
Specular reflection
Diffuse reflection: most objects have rough surfaces (paper or balloon), when parallel lines hit the uneven surface they reflect in all directions (light rays do not respect the laws of reflection)

22. Reflection cont.
Specular reflection: light contacts a perfectly smooth surface (ex: mirror), rays follow laws of reflection
When parallel light rays contact a smooth surface their reflection is parallel
Producing a true mirror image

23. Reflected image
Image appears to be behind the mirror at the same distance as the reflected object
AKA Virtual Image (made by the prolongation of reflected rays) not the real rays!!
Real Image is made by real crossing of light rays
Image is the same size as object
Image is horizontally inverted (the left is now the right side)

24. Reflected Image pg. 109
Can localize Virtual image beyond plane of mirror by drawing incident rays from the object and the resulting rays
Image produced at the meeting point of the prolongation of the reflected rays
Fig 4.31

25. Plane mirrors Change the trajectory of light rays by reflection
Increase the observer’s field of vision
Think of a review mirror on a car, or the mirror your dentist uses
They change the trajectory of light rays so the rays can reach the eye of the observer

26. Refraction
Refraction: the deviation of light ray as it passes from one transparent medium to another (ex: air to water)
Fig take a look!
Lenses help to refract light as it passes through them

27. Lenses Lenses: 2 types of lenses:
objects made up of transparent materials
have at least one curved surface
ability to refract light as it passes through them
2 types of lenses:
Converging
Diverging

28. Focal points
There are 2 focal points between diverging and converging lenses
Principal Focal Point (F)
Secondary Principal Focal Point (F1)
Pg 112 look at the images

29. Converging Lens

30. Converging lens
Focal point of converging lens real point where the refracted rays actually meet when the incident rays run parallel
Ex: magnifying glass

31. Diverging Lens

32. Diverging lens
Focal point of diverging lens is the virtual point from which the refracted light rays appear to emanate when the incident rays run parallel

33. Applying what you know…
Pg. 114 image has many outcomes, lets look at them all...
Pg. 115 image is virtual and smaller than object