Ch. 24 Waves, Sound, Light Section 1 Waves A disturbance that moves through matter or space and carries energy Matter does not move from place to place. Energy transfers through the matter. Think of the wave in a stadium. The people (matter) do not change seats, but the energy travels around the stadium.

Transverse waves A mechanical wave (Can only move through matter) Causes particles to move back and forth at right angles to the direction of the wave motion. crest trough

Compression Waves A mechanical wave (through matter only) Causes particles to move back and forth along the same direction in which the wave is moving.

Electromagnetic Waves Can travel through empty space. Transverse Waves Light waves X rays Radio waves Infrared waves Contain electric and magnetic part.

Electromagnetic Wave

Wavelength The distance between two like points on a wave. wavelength

Compression Wave Wavelength

Frequency The number of wavelengths that pass a point each second. Count the crests or troughs Count the compressions or rarefactions 1 second

Frequency equals……. 6 wavelengths / second 6 λ / s 6 hertz 6 Hz

Amplitude The amount of energy that a wave carries. Higher crests on a transverse wave. Tighter compressions on a compression wave.

Amplitude measured from the midline to a crest or trough.

Law of Reflection The angle of the incoming wave will equal the angle of the outgoing wave. normal

Refraction Waves travel at different speeds depending on the properties of the material they are traveling through. Causes the wave to change direction.

Diffraction The bending of waves around an object. Do shadows have crisp edges? If so, when? Shadow of hand on desk? Any light?

Diffraction: Look at the edges!

Wave Speed Electromagnetic waves: light waves Travel fastest: Space Air (gas) Water Transparent solid Mechanical Waves: compression/transverse Solids Air Do not travel through space

Section 2 Sound Waves Sound Waves = Compression Waves Cannot travel through empty space. Travel fastest through solids, then liquids, then gases.

Sound intensity Amount of energy carried by the wave. Measured by the amplitude.

Frequency and Pitch. Pitch The human perception of the frequency of sound. Sounds with a low pitch have a low frequency. Sounds with a high pitch have a high frequency.

The Human Ear Outer Ear Visible ear and ear canal. Compression wave funnel Cup your hand around your ear?

Middle Ear Sound amplifier Eardrum 3 smallest bones in the body Tiny membrane that acts like a drumhead and vibrates with the compression waves. 3 smallest bones in the body Hammer - Malleus Anvil - Incus Stirrup - Stapes

Inner ear The sound converter The amplified compression waves travel from the stirrup to the cochlea. Cochlea Fluid filled Snail shell shaped organ lined with billions of tiny hairs. Hairs convert compression waves into nerve impulses. Nerve impulses travel through auditory nerve to brain where they are interpreted as sound. Semi Circular Canals: Acts as device to keep a human balanced.

The Human Ear

Sound reflection Reverberations Echolocation Echoes Sounds that reflect Echolocation Process of locating objects by bouncing sounds off of them. Bats, Dolphins, Whales

Homework Find the speed at which sound travels in feet/second in air. Describe the path of a sound wave from my voice box to your brain. Begin with the origination of the energy and end with you understanding what I say. One paragraph with correct grammar. Will be collected. 10 pts.

Section 3 Light Waves

Light Waves are….. Electromagnetic waves Can travel through matter or space Able to travel up to 185,000 miles/s in empty space. Able to travel from the sun to earth (150 million km) in 8 minutes. Able to travel the fastest in empty space and the slowest in solids. (glass)

Electromagnetic light wave

The electromagnetic spectrum Increasing Energy Decreasing wavelength

ROY G BIV R O Y G B I V

Infrared and Ultraviolet Infrared waves Have less energy than red light waves Infra = lesser Ultraviolet waves Have more energy than violet light waves Ultra = more Harmful to skin and eyes.

The human eye.

How we see! Light waves reflect off of an object. Reflected light waves enter eye through cornea. Transparent layer of outer eye. Waves pass through the pupil. Opening in the eye controlled by the iris. Waves then pass through the lens. Flexible disc that changes shape to allow you to focus on near and far objects. Lens focuses waves on retina. Back wall of the eye.

Retina Contains over a hundred million light sensitive cells. Rods Sensitive to dim light Help us to see in darkness. Cones Enable us to see colors. 3 types Red/yellow Green/yellow Blue/violet

Image of rods and cones in retina.

Let’s see.

Nearsighted vs. Farsighted. Cannot see objects far away. Image focused to NEAR to the lens. Farsighted Cannot see object that are close. Image focused to FAR from the lens.

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