1. Spectra of Science Amole 2013
Sound and Light
Spectra of Science
Amole
2013

3. Sound Waves Produced from vibrating particles
Particles “bump” into each other to transfer the energy through the medium
Travel in longitudinal waves
Travel in all directions (like a circle)
Can travel through solids, liquids, and gases
Faster in solids and liquids than gases
Cannot travel in a vacuum
(through empty space)

4. Sound Examples Percussion instruments have vibrating membranes
String instruments have vibrating strings
Woodwinds have vibrating reeds
Brass instruments vibrating lips
Your vocal cords are two thin elastic bands that vibrate
Say “ahhhhh” and touch your throat. Feel them?

5. Notice: High frequencies have shorter wavelengths.
Pitch
How high or low a sound is
Determined by frequency of the sound wave
Frequency is determined by how quick or slow the particles vibrate
Slow Vibration
Low Frequency
Low Pitch
Quick Vibration
High Frequency
High Pitch
Notice: High frequencies have shorter wavelengths.

6. Intensity
Determines the “loudness” of the sound
Intensity decreases with distance from the sources as it spreads out
Depends on the amplitude of the sound
Higher amplitudes produce louder sounds
Louder
Softer
Notice: The wavelength and frequency are the same. Only amplitude changed.

7. Hearing Sound: The Ear
3 bones: hammer, anvil, and stirrup
Sound causes your eardrum to vibrate. The eardrum vibrates differently for each sound.
The bones of your ear begin to vibrate, beginning with the hammer, moves to the anvil, and finally the stirrup
Eardrum

8. Hearing Sound: The Ear
Cochlea
Outer Ear
The sound energy passes to the inner ear. This causes the fluid in the cochlea to move.
The nerves then carry the message to the brain. Your brain then tells you what the sound is.
Inner Ear

9. Producing Sound: The Vocal Chords
Air from the lungs flows through the windpipe and into the voice box (where the vocal cords are).
Then the air pushes the vocal cords apart making them vibrate.
3. The vibrations create a series of sound waves that exit through your mouth.

10. Producing Sound: The Vocal Chords
The change of shape of the vocal cords changes the sound and its pitch.
If you can’t talk because of a cold or laryngitis, it is because your vocal cords are swollen and inflamed.

11. More About Sound Sonar- Sound Navigation And Ranging Ultrasound
Determine distance by measuring the time it takes for sound waves to be reflected back
Used by ships, submarines, and bats
Ultrasound
Use echos to produce images called sonograms of inside the body without performing surgery

12. Did You Know?
Sound waves that are reflected off boundaries are called “echos.”
Sound travels 4 times faster in water than air.
Any frequency of sound below the range of human hearing (20 Hz) is called Infrared sound.
Any frequency of sound above the range of human hearing (20, 000 Hz) is called Ultrasound.

13. Doppler Effect
Change in frequency of a wave due to relative motion between source and observer.
A sound wave frequency change is noticed as a change in pitch.

15. Light Waves “Dual natured” Travel in transverse waves
Travel in straight lines in all directions
Can travel through some solids, liquids, and gases
Slow down when traveling through a medium
Can travel in a vacuum (through empty space)
Consist of changing electric and magnetic fields in space

16. Where does light come from?
Our major light source:
the Sun

17. Electromagnetic Spectrum

18. Two Models of Light Wave Model Stream of Particles Model
Transverse waves that do not need a medium
Explains why light can reflect, refract, or diffract, interfer with one another, and produce standing waves
Stream of Particles Model
Photons- packets of light, localized energy
Explains why blue light can knock electrons off a metal plate but red light cannot, and why light can travel without a medium
The model used depends on the situation

19. Energy and Frequency Energy of light is proportional to frequency
Higher frequency = more energy

20. The Speed of Light In a vacuum, all light travels at the same speed
3 x 108 m/s = 186,000 miles/sec
Symbol “c”
Light is the fastest signal in the universe
Also can travel through transparent mediums
Air, water, and gas
Travels slower when passing through a medium
More dense = slower speed

21. Intensity Determines the “brightness” of light
Intensity decreases with distance from the sources as it spreads out
Depends on amount of light (number of photons or power passing through)

22. Intensity

23. How Light Travels
Light rays travel in straight lines from the light source.
When it hits an opaque object, some light is absorbed and the rest reflects off.
If the object is transparent, light rays pass through it easily.
If the object is translucent, some light can pass through, but the rest of the light will be reflected.

24. The ‘angle of reflection’ is always equal to the ‘angel of incidence’.
off
Angle of incidence
Angle of reflection
The ‘angle of reflection’ is always equal to the ‘angel of incidence’.

25. Only red light is reflected
Seeing Color
The colour an object appears depends on the colours of light it reflects.
For example, a red book only reflects red light:
Homework
White
light
Only red light is reflected

26. Colors
White light can be split up to make separate colours. These colours can be added together again.
The primary colours of light are red, blue and green:
Adding blue and red makes magenta (purple)
Adding blue and green makes cyan (light blue)
Adding red and green makes yellow
Adding all three makes white again

27. A white hat would reflect all seven colours:
A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):
Purple light
A white hat would reflect all seven colours:
White
light

28. Refraction Waves travel different speeds in different mediums
When waves change mediums, their speed changes causing the waves to bend

29. Diffraction
light
source
light
source
Light rays travel in straight lines, radiating out from the light source.
If rays are blocked by an opaque object a shadow forms where the light cannot reach.
If the light source is moved closer to the object, more light is blocked and a larger shadow is formed.

30. Shadows Looking North, the Sun appears to rise in the East...
12am
Looking North, the Sun appears to rise in the East...
2pm
10am
The position of the Sun effects the position and length of the shadows created.
9am
3pm
8am
4pm
6am
7pm
Thanks to this natural phenomenon a sundial is able to tell us the time, as long as it is a sunny day!
...and travel across the sky until it sets in the West.

31. Seeing Light: The Eye
Light coming from, (or reflecting off) objects enters the eye through the cornea then the pupil.
It is focused clearly by the lens on to the retina.
The light sensitive cells of the retina gather information about patterns of light and dark, color and movement and send it through the optic nerve.

32. Seeing Light: The Eye
Information entering the brain through the optic nerve, is then transmitted through more nerve pathways to the visual cortex.
Here the patterns of light and dark, colour and movement are interpreted.
The brain, based on past experience, can then understand what it ‘sees’.

33. More about Light Sunlight contains ultraviolet and infrared
UV will burn you, IR warms you
X-rays and gamma rays are high frequency light waves used in medicine
Microwaves are used in cooking and communication (mobile phones)
Radio waves are used in communication and radar
Radar: Radio Detection And Ranging
Uses reflected radio waves to determine velocity and location

34. Did You Know?
Rainbows are the refraction of white light through water droplets that reflect them back in the air.
Fiber optics operate on total internal reflection.
The interference of light waves create the rainbow swirls on bubbles.
The light we see from the sun is 8 minutes old. It takes light 8 minutes to travel from the sun to Earth even at its fast speed.