WAVES

SN#1 What are waves? Wave – a disturbance that transfers energy from place to place. Medium – the material thru which a wave passes Waves travel through the medium without actually moving the medium with it.

Parts of a Wave Crest – the highest point of the wave Trough – the lowest point of the wave Wavelength – distance between one point on the wave and the same point on the next consecutive wave Amplitude – The measure from the rest point to the crest or trough. The amplitude is a measure of how much energy is in the wave Sound amplitude = volume

Crest Wavelength Amplitude Trough

Amplitude and Frequency SN #2 Amplitude and Frequency

What information about waves do amplitude and frequency provide 3 measurable properties of waves 1. Amplitude 2. Frequency 3. Wavelength Amplitude is an important measurement because it tells you how much energy the wave has. In a sound wave, amplitude = volume Frequency is how many waves pass a given point in a certain amount of time. Frequency is measured in Hertz (Hz), which is how many waves per second. In a sound wave, frequency = pitch

Relationships between………. Amplitude and Frequency = none Frequency and wavelength = inverse when wavelength increases, frequency decreases. As wavelength decreases, frequency increases. Same amplitude – different wavelength

What are Mechanical Waves? SN#3 What are Mechanical Waves? Mechanical Waves are waves that must have a medium to travel through. Medium = matter The denser the medium the faster the wave travels. Mechanical waves come in 2 forms: Transverse Longitudinal/Compression

Transverse Waves Mechanical Waves where the particles of matter in the medium vibrate by moving back and forth and perpendicular (at right angles) to the direction the wave travels Examples: Ocean Waves Seismic Waves

Longitudinal/Compression Waves Mechanical waves in which the particles of matter in the medium vibrate by pushing together and move apart parallel to the direction in which the wave travels. Examples: Sound Waves Waves on a spring

What are the Characteristics of Sound SN#6 What are the Characteristics of Sound Sound is a form of energy that travels as Longitudinal/Compression waves. Sound waves are produced by vibrations. Characteristics of sound include volume which is determined by amplitude and pitch which is determined by wavelength.

High Frequency sounds have a short wavelength. Objects vibrate quickly = High Pitch Low Frequency sounds have a long wavelength. Objects vibrate slowly = Low Pitch High Pitch Sounds Low Pitch Sounds Bats Flute Whistle Pipe Organ Fog Horn Frog Croak

What happens when sound is reflected & absorbed? SN#7 What happens when sound is reflected & absorbed? Sound wave behavior is influenced by the medium through which it is traveling. Sound can be reflected, absorbed, diffracted and refracted.

Reflection Sound waves can be reflected when a sound wave hits a barrier and bounces back. Usually this happens when a sound wave hits a smooth flat surface. This produces an echo

Absorption Sound waves can be absorbed when a sound wave causes particles to vibrate which absorbs the sound and changes the sound to heat

What happens when sound is Diffracted and Refracted? SN#8 What happens when sound is Diffracted and Refracted? Sound waves can be refracted and diffracted. Both refraction and diffraction have to do with bending the wave.

Refraction In refraction waves are bent because the pass from one medium to another which changes their speed and wavelength causing them to bend. This happens when we hear through a wall.

Diffraction In diffraction, there is a change in the direction of waves as they pass through an opening or around a barrier in their path.  Sound diffracting around corners or through door openings, allowing us to hear others who are speaking to us from adjacent rooms

How is sound present in daily life? SN#9 How is sound present in daily life? Oscilloscope – A device used to “record” sound Ultrasound – sounds above which humans can hear. (20-20,000 Hz) Ultrasound is used to create images inside the body which are difficult to see. Ultrasounds are used to create pictures of organs like Kidneys and Heart.

Sonic Toothbrush – uses ultrasound to break plaque off teeth Sonar – used to create images of the ocean floor. Doppler Effect – The Doppler Effect is a phenomenon that occurs when the pitch changes because either the listener or the source of the sound is moving. As the sound moves closer the wavelength (wl) becomes compressed = short wl

Short wl = High Pitch After the source of the sound passes, wl is longer = lower pitch

What are Electromagnetic (EM) Waves SN#12 What are Electromagnetic (EM) Waves Electromagnetic waves are everywhere. These waves can travel through a vacuum. EM waves have many different wavelengths The shorter the wavelength - the higher amount of energy they transmit.

All EM waves travel at the speed of light – 300,000 Km/s or 186,000 mi/s EM waves have found valuable uses in our lives The EM spectrum is all wavelengths of EM energy.

The Electromagnetic Spectrum

Radio Waves *Longest Wavelength *Lowest Frequency *Lowest Energy Examples-TV signals, AM & FM radio signals Radio waves travel easily through the atmosphere and many materials.

Microwaves *Shorter Wavelength than Radio Waves *Higher Frequency than Radio Waves *Higher Energy than Radio Waves Examples-Cell Phones and Radar Microwave ovens produce microwaves that cause water molecules in food to vibrate faster, which makes food warmer.

Infrared Waves *Shorter Wavelengths than Microwaves *Higher Frequency than Microwaves *Higher Energy than Microwaves Examples- Sun, Fire and Radiator All objects emit infrared waves-usually given off by hot objects (stars, lamps, people and animals). Infrared radiation is the type of EM wave most often associated with heat.

Visible Light *Shorter Wavelength than Infrared Light *Higher Frequency than Infrared Light *Higher Energy than Infrared Light Examples that reflect visible light: Sun, Light Bulbs Visible Light is the only part of the EM spectrum that the human eye can see. Red light= longest wavelength; lowest frequency Violet light= shortest wavelength; higher frequency White light= all colors mixed together

Ultraviolet Light *Shorter Wavelength than Visible Light *Higher Frequency than Visible Light *Higher Energy than Visible Light Examples-Sun and special lamps (tanning bed) The wave can damage your skin and eyes; sun block can help filter out these frequencies. Uses: Sterilize medical equipment, help the produce vitamin D, harden dental fillings, and tanning.

X-Rays *Shorter Wavelength than Ultraviolet Light *Higher Frequency than Ultraviolet Light *Higher Energy than Ultraviolet Light Examples- X-ray machines to view bones and airport security X-rays have enough energy to go through skin and muscle but are absorbed by the bone. Can be dangerous for a living organism.

Gamma Rays *Shortest Wavelength *Highest Frequency *Highest Energy Examples- Sun, other stars and radioactive substances Used to kill cancer cells and fight tumors. Can be dangerous for a living organism.

SN # 13 What happens when EM waves are reflected and absorbed The behavior of light waves (EM waves) can be manipulated by the medium through which they travel. Reflection and absorption are two possible manipulations.

Reflection Reflection of light occurs when EM waves (which light is a part) strike a barrier and bounce back. It is light that is reflected which the human eye sees.

The Law of Reflection states that the angle of incident equals angle of reflection.

Absorption This is when an EM wave disappears into a medium by changing to keep energy. Darker Colors absorb EM waves Lighter Colors Reflect EM waves.

SN # 14 What happens when EM waves are Diffracted and Refracted EM waves can be manipulated. Diffraction and Refraction cause the waves to bend and change speed.

Refraction Occurs when EM waves encounter a new medium causing the waves to bend. Your eyes refract light in order to focus the light on your retina. Light bends when it goes from air to water. This is why a straw in water looks broken.

Diffraction Occurs when EM waves bend around a barrier or opening. This is why shadows look fuzzy.

SN #15 How are Mechanical and EM waves similar and different? Mechanical Waves Reflect, absorb, refract, diffract Travel as longitudinal/ compression waves Travel through A vacuum Carry energy Travel at the same speed= 300,000km/sec Travel in a medium Have amplitude, wavelength, frequency Travel at different speeds Travel as Transverse waves Have many valuable uses Many different wavelengths

SN#16 How does the human eye see color? The human eye gathers and focuses light. The eye sees the color that is reflected. The color of light is determined by the wavelength. Light travels through the eye from the cornea, through the pupil, through the lens and strikes the retina.

*The cornea and lens refract light in the eye. *Pupil size, controlled by the iris, determines how much light enters the eye. *Light strikes the retina, forming a small inverted image. The brain receive signals from the retina and interprets the image right side up.

*The retina has cells called rods that distinguish brightness- black and white The retina also has cones that detect color. The vitreous humour is the clear gel that fills the space between the lens and the retina

VITREOUS HUMOUR

Structure & Function IRIS colored part of eye controls light entering PUPIL black hole in iris where light enters

Structure & Function SCLERA whites of the eye supports eyeball provides attachment for muscles LENS converging lens allows us to see objects near and far

Structure & Function CORNEA RETINA transparent bulge over pupil focuses light (refracts) onto retina RETINA internal membrane contain light-receptive cells (rods & cones) converts light to electrical signal

Structure & Function OPTIC NERVE Transmits electrical impulses from retina to the brain Creates blind spot Brain takes inverted image and flips it so we can see

Blind Spot On retina where optic nerve leads back into the brain No rod or cone cells Other eye compensates for this area Try this test to prove you have a blind spot…

Close left eye and approach screen while staring at the letters…watch the dot!

Structure & Function RODS CONES 120 million cells detect brightness (black & white) for night vision CONES 6 million cells detect colour (RGB) GANGLION CELLS Detect movement and patterns

Normal Eye Focus “Blind spot”

Video YouTube “The Human Eye” and “How the Human Eye Works” https://www.youtube.com/watch?v=yzyphSTkW2U

The Human Eye Refractive index of lens different for each wavelength (colour) Cool colours (blues) appear closer; warm colours (reds) further away Agree?

Others see the opposite. Most people see the red, Closer than the blue. Others see the opposite. How about you?

Are you seeing spots?

Are these lines bent….?

…or straight?

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