Science Wave Unit

Surface waves

- Particles undergo a circular motion - Not truly transverse or compressional Example: water waves

Ultra-Violet rays

-Emitted by the sun -Produces Vitamin D in human skin..so it's GOOD (in small amounts) -Overexposure causes sunburn and can burn the retina of the eye -Used for sterilization because it can kill bacteria -Visible to INSECTS

High to Low Energy

-Gamma -X-ray -UV -Visible -Infrared -Microwave -Radio

Interference

-When two or more waves meet, they interact with each other -The interaction of waves with other waves is called wave interference -Interference usually happens when two waves traveling in opposite directions meet, and their amplitudes are temporarily changed

wave behavior

1. Reflection 2. Refraction 3. Diffraction 4. Interference 5. Standing waves 6. Resonance

diffraction

Diffraction occurs when an object causes a wave to change direction and bend around it

Infra-red rays

EM waves felt as thermal energy or warmth Hotter objects emit more waves than cooler objects Infra-red waves penetrate darkness, clouds, mist, etc. Used in military, remote controls

electromagnetic waves are different because?

Electromagnetic waves are unique in that they DO NOT need a medium to travel in. They are capable of traveling in a vacuum

Volume

Human perception of sound volume, depends on intensity Intensity measured in decibels, dB

Diffuse Reflection

Rough surfaces diffuse a beam of light because each individual ray meets a surface which has a different orientation, and the ray must obey the law of reflection

medium

The medium is the material through which a wave travels

Visible Light

White light - combination of all colors In order of wavelength - ROY G. BIV

pulse

a one-time disturbance

Speed formula

(wavelength, λ )(frequency, ƒ) s = λƒ units = m/s

Constructive Interference

-Crests of one wave overlap with the crest of another wave -As the waves pass through each other, the crests combine to form a wave with a greater amplitude

Elasticity affects sound speed

-Elastic objects tend to rebound quickly when sound waves pass through them -Solids are usually more elastic than liquids and gases

X-rays

-High energy EM waves -Penetrate soft flesh but not bone. -Prolonged exposure damages body tissues. Why? High Energy!

Pitch

-How high or low a sound seems to be -Related to frequency -High frequency = high pitch -Low frequency = low pitch

Wave / Particle Duality

-Light acts as both a wave and a particle -What we detect depends on the method we use to study it: The beautiful colors that appear in a soap film or in the dispersion of light from a diamond or prism is also best described as waves -The light that strikes a solar cell to produce an electric current is best described as a particle -Video

Electromagnetic waves

-Made by vibrating electric and magnetic fields that transfer energy as they travel through space -EM radiation travels across space in the form of waves -the distance from one point to the next point

Radio Waves

-Radio stations -Low frequency EM waves with wavelengths from less than a centimeter to about 1000 meters -TV Channels -Cell Phones -Radar -MRI

Reflection

-Reflection occurs when a wave strikes an object and bounces off of it -All types of waves can be reflected -The angle of incidence of a wave is always equal to the angle of reflection

Specular vs. Diffuse Reflection

-Reflection off of smooth surfaces such as mirrors or a calm body of water is known as specular reflection -Reflection off of rough surfaces such as clothing, paper, or the asphalt roadway is known as diffuse reflection

Why are sunsets RED?

-Since the BIV portion of the spectrum is scattered by nitrogen and oxygen, the ROY portion of the spectrum is able to pass through the atmosphere and reach our eyes in a non-interrupted path -Sunlight tends to be most rich in yellow frequencies, which is why the sun appears yellow during the day -During sunset, however, the sun approaches the horizon line and must travel a greater distance through our atmosphere

Why is the sky blue?

-The atmosphere is a gaseous sea that contains a variety of particles, most notably gaseous nitrogen and oxygen -Nitrogen and oxygen are effective in scattering the high frequency, short wavelength portion of the visible light spectrum - Human eyes sensitive to blue, not violet freque

Temperature affects sound speed

-The speed of sound through gases and fluids is impacted by temperature -As the temperature increases, sound waves travel faster

Gamma Rays

-Ultra high frequency EM waves that can travel through matter, break molecular bonds, and damage cells -Used for radiation therapy

Standing Waves

-Waves may reflect off an obstacle that they are unable to pass through -When waves are reflected straight back from an obstacle, the reflected wave has the same wavelength, amplitude, and frequency as the original- but is traveling in a different direction. -The reflected wave will interfere with the original wave and create what's called a standing wave. -Standing / stationary waves have points called nodes where the wave appears to be still

Why is some light invisible to us?

-We have rods and cones in our eyes that can only detect certain wavelengths of light. -Other animals have different receptors that receive different wavelengths of light- which is why insects can see infrared light but we cannot.

Destructive Interference

-When the crests of one wave overlap the troughs of another wave -As the waves pass through each other, the crests and troughs cancel each other out to produce a wave with zero amplitude

what are the three different mechanical waves?

1- Transverse wave 2- Longitudinal wave 3- Surface wave

How do waves differ?

1. How much energy they carry 2. How fast they travel 3. How they look

wave properties

1. Molecules pass energy on to neighboring molecules 2. Waves carry energy without transporting matter 3. All waves are produced by something that vibrates

amplitude of compression is related to?

Amplitude of compression waves is related to how tightly the particles are pushed together at the compression Denser compressions = larger amplitude

Congressional waves differ because?

Congressional waves have dense regions called compression's and less dense regions called rarefaction

frequency

Frequency = number of waves that pass per second Measured in Hertz (Hz). *ƒ = how often something (usually waves) happens in 1 second, measured in Hz*

what happens if the wavelength is long?

If a wavelength is L-O-N-G, FEW waves will hit per second

what happens if the wavelength is short?

If a wavelength is SHORT, MANY waves hit per second.

longitudinal waves

Longitudinal waves, also called compression waves, occur when particles in the medium move parallel to the direction that the wave moves Example: Sound waves

Amplitude

Measures the energy in a wave "From rest to crest"

mechanical waves

Mechanical waves require a medium to transmit their energy.

Speed of Sound

Overall, sound moves the fastest in solid mediums, like steel, because the molecules are densely packed together. But there are other factors that affect the speed of sound ...

In longitudinal waves how do particles move?

Particles move side-to-side

In transverse waves how do particles move?

Particles move up & down

Surface waves

Particles undergo a circular motion Not truly transverse or compressional Example: water waves

Density affects sound speed how?

Sound moves faster through solids and slower through gases. This is because the individual particles that make up solids are closer together than particles that make up gases- so the energy is easily transferred.

Period, T

T = the time it takes for ONE of those somethings (waves) to happen, measured in seconds T = 1 / frequency

Resonance

The ability of an object to vibrate by absorbing energy at its natural frequency

Wavelength, λ

The distance between one point in the wave and the nearest point just like it (units = m)

The Electromagnetic Spectrum

The entire range of electromagnetic wavelengths is called the electromagnetic spectrum

Transverse waves differ because?

Transverse waves have crests (high points) and troughs (low points)

Transverse waves

Transverse waves occur when particles of the medium move in a direction perpendicular to the direction that the wave moves Example: Stadium waves

Intensity = Volume

Turning up speaker = increasing intensity Turning down speaker = decreasing intensity

Wave speed depends on?

Wave speed depends on the properties of the medium, such as: -Solid, liquid, gas -Density -Temperature -Elasticity (tension)

Wave speed is NOT AFFECTED BY?

Wave speed is NOT AFFECTED BY WAVELENGTH OR FREQUENCY!!!!!!!

wave

a repeating disturbance or movement that transfers energy through matter or space

Wavelength formula

speed / frequency λ = s / ƒ units = m

Frequency formula

speed / wavelength ƒ = s / λ units = Hz ƒ = 1 / period

Intensity

the amount of energy that passes through a certain area in a given time

Elasticity

the tendency of an object to rebound to its original state when deformed