1. SOUND, LIGHT, MIRRORS & LENSES

2. Sound

3. Sound waves compressional waves formed from vibrating objects colliding with air molecules
* Remember compressional waves are made of two regions called compressions and rare factions

4. Speed of sound
depends on temperature and state of medium
sound travels faster in solids and liquids – molecules are closer together than gas molecules
as medium temp rises, molecules move faster conducting sound waves faster

5. Human Hearing
involves 4 stages:
Stage 1: ear gathers compressional waves which vibrate a tough membrane called eardrum
Stage 2: the middle ear has three bones called hammer, anvil and stirrup which amplify sound wave
Stage 3: the inner ear contains the cochlea which vibrate sending auditory nerve impulses to brain
Stage 4: brain decodes and interprets nerve impulses

6. Intensity amount of energy that flows through a certain area in a given amount of time
Loudness
human perception of sound intensity which is measured in decibels
Pitch
how high or low a sound seems to be which is related to frequency of sound wave
SUBSONIC
HUMANS CAN HEAR
ULTRASONIC
< 20 Hz
20 – 20,000 Hz
> 20, 000 Hz

7. Music and Uses of Sound

8. Music
made of sounds that are deliberately used in a regular pattern
Sound quality
differences among sounds of the same pitch and loudness - that’s why a piano sounds different than a flute playing the same note.
Each instrument has a set of natural frequencies at which it will vibrate called overtones which produce an instruments distant sound quality.

9. Instruments use resonates, or hollow chambers that amplify sound when air inside vibrates. Ex. Brass & woodwinds – mouthpiece; guitars & violins – hollow body; drums – inside and sides
USES OF SOUND
Acoustics – the study of sound
Example. concert hall engineers

10. Echolocation
process of locating objects by emitting sounds and interpreting the reflected sound waves
Example. Bats
Sonar
system that uses the reflection of underwater sound waves to detect objects
Example. fishing boats

11. Ultrasound
high frequency sound waves
Example. medicine – pregnancy, breaking up kidney stones

12. Reflection and Refraction of Light

13. Objects MUST reflect light in order to be seen.
Opaque
does not allow light to pass through - only absorbs & reflects
Translucent
some light
passes through
Transparent
transmits almost
all light absorbing
and reflecting little

14. Law of Reflection
the angle of incidence (i), or where light strikes a surface, is equal to angle of reflection (r)
Regular Reflection
Diffuse Reflection i r
ROCK WALL (ROUGH SURFACE)
MIRROR (SMOOTH SURFACE

15. SUNLIGHT Refraction of light
occurs when wave of light passes from one medium to another and light wave is bent or refracted
Index of Refraction
indicates how much a material reduces the speed of light; the more light slowed, the greater the index of refraction
Water droplet (Rainbow)
*Prisms separate white light into spectrum
* Light refracted through air layers of different densities can result in mirages
SUNLIGHT

16. Mirrors

17. Light is necessary for eyes to see – light waves spread in ALL directions from a light.
Mirror
smooth surfaces that reflect light to form images
Plane Mirror
flat, smooth mirror in which an image appears upright

18. Concave Mirror
mirror surface is curved inward; image depends on location of objective relative to focal point.
Convex Mirror
mirror curved outward, diverge light rays when reflected and show virtual images

19. Image: Upright Or Upside Down
Mirror
Shape
Position Of Object
Virtual /Real
Image: Upright Or Upside Down
Size
Plane
Object At Any Position
Virtual
Upright
Same As Object
Concave
Object More Than 2 Lengths Focal From Mirror
Real
Upside Down
Smaller Than
Object
Object Between One And Two Focal Lengths
Larger Than
Object At Focal Point
None
Object Within
Focal Length
Convex
Subject At Any Position

20. Lenses and Optical Instruments

21. transparent material with a curved surface that reflects light rays
Lens
transparent material with a curved surface that reflects light rays
Lens Shape
Location Of Object
Virtual/R eal
Upright/ Inverted
Size
Convex
Object Beyond 2 Focal Lengths
Real
Inverted
Smaller Than Object
Object Between 1 And 2 Focal Lengths
Larger Than Object
Object Within 1 Focal Length
Virtual
Upright
Concave
Object At Any Position

22. Structure of your eye allow you to focus on objects Light enters eye through cornea, a transparent covering on the eyeball.
A convex lens helps to focus light rays to form images.
The retina, or inner lining of eye converts light into electrical signals that brain interprets

23. Telescopes
use mirror and lenses to gather more light from far away objects than the eye does.
Microscopes
uses two convex lenses with short focal lengths to magnify small, close objects

24. Cameras
gathers and bends light with a lens to form an image on light – sensitive film