# Waves carry energy from one place to another.

## Presentation on theme: "Waves carry energy from one place to another."— Presentation transcript:

Waves carry energy from one place to another.
Waves have characteristic properties that do not depend on the type of wave. 1 2 3 4 5 6 7 Waves carry energy from one place to another. Transverse and longitudinal waves exist in mechanical media, such as springs and ropes, and in the Earth as seismic waves. Wavelength, frequency and wave speed are related. Sound is a longitudinal wave whose speed depends on the properties of the medium in which it propagates. Radio waves, light and X-rays are different wavelength bands in the spectrum of electromagnetic waves, the speed of which in a vacuum is approximately 3 x 108m/s, and less when passing through other media. Waves have characteristic behaviors, such as interference, diffraction, refraction and polarization. Beats and the Doppler Effect result from the characteristic behavior of waves.

Are these the same things?
What are they? Are these the same things? Radio Waves Microwaves Infrared Visible Light Ultraviolet Light X-rays Gamma Rays Before we answer that question, lets review some metric units & scientific notation.

normal units without prefixes
Symbol Value Description pico p 10-12 1 picometer, (pm) = m nano n 10-9 1 nanometer, (nm) = m micro µ or u 10-6 1 micrometer (µm) = m milli m 10-3 1 millimeter (mm) = m centi c 10-2 1 centimeter (cm) = 0.01 m deci d 10-1 1 decimeter (dm) = 0.1 m NONE 1 normal units without prefixes kilo k 103 1 kilohertz (kHz) = 1000 Hz mega M 106 1 megahertz (MHz) = 1,000,000 Hz giga G 109 1 gigahertz (GHz) = 1,000,000,000 Hz tera T 1012 1 terahertz (THz) = 1,000,000,000,000 Hz

 Are all parts of the electromagnetic spectrum
Radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays  Are all parts of the electromagnetic spectrum and are fundamentally the same thing. They are all electromagnetic radiation. The electromagnetic spectrum can be expressed in terms of wavelength, frequency, or energy.

v = f x λ v = f x λ 340 m/s = speed of sound
300,000,000 m/s = speed of light 3*108 m/s = 3*105 Hz x 1*103 m v = f x λ

v = f x λ c = 3×108 m/s (Approximate Value)
340 m/s = speed of sound 300,000,000 m/s = speed of light c = 3×108 m/s (Approximate Value) Speed of light in a vacuum 299,792,458 m/s (1,079,252,849 km/h)

Lower Energy Higher Energy Energy E = h x f
(Planks Constant) h = 6.626 × 10-34 joule·seconds h = x eV·seconds 1 eV = ×10−19 J.

Energy in Electro Magnetic Waves
E = h x f h = 6.626 × 10-34 J·sec (Planks Constant) EM Wave Freq (Hz) h x f = E Energy Television 108 Hz (6.626 x 10-34) x (108) 6.6 x10-26 J Infrared 1014 Hz (6.626 x 10-34) x (1014) 6.6 x10-20 J Ultra Violet 1016 Hz (6.626 x 10-34) x (1016) 6.6 x10-18 J X-Rays 1018 Hz (6.626 x 10-34) x (1018) 6.6 x10-16 J What about a Microwave at 3,000 MHz (3.0 x 109 Hz)?

E = h x f KE = ½ mv2 994,000 J = ½ * 1179 Kg * 41 m/s
If a single microwave (photon) has a frequency of 3,000 MHz, how much energy will it have? E = h x f h = 6.626 × 10-34 J·sec E = (6.626 × 10-34 J·sec) x (3.0 x 109 Hz) E = 1.99 x J per photon EM (Hz) Energy TV 108 Hz 6.6 x10-26 J IR 1014 Hz 6.6 x10-20 J UV 1016 Hz 6.6 x10-18 J X-Rays 1018 Hz 6.6 x10-16 J NOTE: a 1KW microwave oven with a frequency of 2999 MHz produces 5.0 x 1029 photons per second. E = (1.99 x J) x (5.0 x 1029) = 994,000 J per second KE = ½ mv2 Note: most microwaves operate at 2,450 MHz not 2,999 MHz 994,000 J = ½ * 1179 Kg * 41 m/s 994,000 J = ½ * Toyota * 90 mph

Radio Waves - Longest wavelengths in the EM spectrum
Cellular 100 kHz 1 GHz Waves can be longer than a ten football fields or as short as a football. Radio waves can penetrate the earths atmosphere – radio astronomy The above image shows the Carbon Monoxide (CO) gases in our Milky Way galaxy.

Radio Waves - Common frequency bands include the following:
-AM radio kilohertz to 1.7 megahertz -Short wave radio - bands from 5.9 megahertz to 26.1 megahertz -Citizens band (CB) radio megahertz to megahertz -Television stations - 54 to 88 megahertz for channels 2 through 6 -FM radio - 88 megahertz to 108 megahertz -Television stations to 220 megahertz for channels 7 through 13 Every wireless technology you can imagine has its own little band: -Garage door openers, alarm systems, etc. - Around 40 megahertz -Standard cordless phones: Bands from 40 to 50 megahertz -Baby monitors: 49 megahertz -Radio controlled airplanes: Around 72 megahertz, which is different from... -Radio controlled cars: Around 75 megahertz -Wildlife tracking collars: 215 to 220 megahertz -MIR space station: 145 megahertz and 437 megahertz -Cell phones: 824 to 849 megahertz -New 900-MHz cordless phones: Obviously around 900 megahertz! -Air traffic control radar: 960 to 1,215 megahertz -Global Positioning System: 1,227 and 1,575 megahertz -Deep space radio communications: 2290 megahertz to 2300 megahertz

Radio Waves - Longest wavelengths in the EM spectrum

100 kHz 1 GHz Centimeters Microwave Ovens Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke. (point - to - point) Shorter microwaves are used in remote sensing. These microwaves are used for radar like the doppler radar used in weather forecasts. Microwaves, used for radar, are just a few inches long Radar is an acronym for "radio detection and ranging"

1 x1012 Hz 4 x1014 Hz 750 nm Special cameras and film that can detect differences in temperature, and then assign different brightnesses or false colors to them. Far infrared waves are thermal. In other words, we experience this type of infrared radiation every day in the form of heat ! The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared Shorter, near infrared waves are not hot at all - in fact you cannot even feel them. These shorter wavelengths are the ones used by your TV's remote control.

Which EM wavelengths can make it through our Atmosphere?
H e a t

Visible light can easily penetrate the atmosphere, Infrared can not penetrate (or escape) as easily.

Color Wavelength violet 380–450 nm blue 450–495 nm green 495–570 nm yellow 570–590 nm orange 590–620 nm red 620–750 nm Though electromagnetic waves exist in a vast range of wavelengths, our eyes are sensitive to only a very narrow band – visible light (approximately 400 – 700 nm)

1 x1015 Hz 3 x1016 Hz Though these waves are invisible to the human eye, some insects, like bumblebees, can see them! 400 nm 10 nm UVA 400 nm – 315 nm (Black Lights) UVB 315 nm – 280 nm (Sun Burn) UVC 280 nm – 100 nm (germicidal) Health concerns for UV exposure are mostly for the range nm in wavelength, the range called UVB. The most effective biological wavelength for producing skin burns is 297 nm A sterilization method that uses ultraviolet (UV) light to break down micro-organisms. (Food, air and water purification.)

We usually talk about X-rays in terms of their energy rather than wavelength.
1 x1016 Hz 1 x1018 Hz Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent. Metal absorbs even more X-rays. Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets!

Many things in deep space give off X-rays
Many things in deep space give off X-rays. Many stars are in binary star systems - which means that two stars orbit each other. When one of these stars is a black hole or a neutron star, material is pulled off the normal star. This materials spirals into the black hole or neutron star and heats up to very high temperatures. When something is heated to over a million degrees, it will give off X-rays! The above image is an artist's conception of a binary star system - it shows the material being pulled off the red star by its invisible black hole companion and into an orbiting disk.

1 x1018 Hz These waves are generated by radioactive atoms and in nuclear explosions. Smallest wavelengths and the most energy of any other wave in the Electromagnetic spectrum. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.

v = f x λ E = h x f Gamma Rays – ENERGITICALLY Interesting Facts
Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime! So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy. The sources of these enigmatic high-energy flashes remain a mystery. Smallest wavelengths Highest frequency Most energy v = f x λ E = h x f By solving the mystery of gamma-ray bursts, scientists hope to gain further knowledge of the origins of the Universe, the rate at which the Universe is expanding, and the size of the Universe.

LIGHT LIGHT LIGHT Visible Light
What is the only thing that we (humans) can see? A very small band of the electromagnetic spectrum between 380 – 750 nm (400 – 700 nm) LIGHT

Sight & Light What is occurring between our eyes and the objects that we see? Is there anything traveling between our eyes and the objects? Rods & Cones send signals to the brain

What do you see? WAIT - Don’t say it out loud.
An electromagnetic wave with a wavelength of approx. 600 nm

All visible wavelengths
What do the EM waves do when they hit an object? White Light All visible wavelengths Until the EM waves hit an object Energy traveling as EM waves through a medium (or a vacuum)

We see the wavelengths of light that are reflected off of the object.
The wavelengths of light we see We see the wavelengths of light that are reflected off of the object. All other wavelengths are absorbed by the object. Daylight - Not a perfect spectrum Reflected light

Do we see all of wavelengths of visible light at the same intensity?
Color absorption by different glass

Did the actual paint on the walls change?
Incandescent bulb Daylight bulb Mercury Lamp Did the actual paint on the walls change? Sodium Lamp (low pressure) Sodium Lamp (high pressure)

What are the wavelengths of these spectral lines?
What is the perceived color of the light source? What are the wavelengths of these spectral lines? Neon Spectrum Perceived color VS actual wavelengths present in the light source. Not every wavelength present Spectral lines

Today’s Lab Determine the wavelengths that are present in six different light sources ||||||||||||||||||||||||||||||||||||||||| | | | | | | | | | | | | | | ||||||||||||||||||||||||||||||||||||||||| | | | | | | | | | | | | | | Lab Report Blue Dark Red Yellow/Orange

Visible Light & Wavelength Wave speed did not change

Colors of Light G R B R + G B + G R + B Green – Magenta Red – Cyan
Simulation – mixing colors of light (over lapping) G R B R + G B + G R + B Green – Magenta Red – Cyan Blue – Yellow

Note that the intensity (the brightness) of each band is different
Helium Spectral Lines – Lab Results Perceived color = pink? ||||||||||||||||||||||||||||||||||||||||| | | | | | | | | | | | | | | ||||||||||||||||||||||||||||||||||||||||| | | | | | | | | | | | | | | Note that the intensity (the brightness) of each band is different

Fluorescent Tube Spectral Lines - Results
Hallway Fluorescent lights Note the differences in intensity

Natural Light (sun light on sky bridge)
400 nm 700 nm Incandescent Bulb (night light) Fluorescent Bulb - older type - (single tube) Fluorescent Bulb - Newer type - (hallway lights) Fluorescent Bulb - Energy Saver - (not in class)

Hydrogen Spectral Lines – Lab Results
400 nm nm nm nm Wavelength (nm) Relative Intensity Transition Color 15 6 -> 2 Violet 30 5 -> 2 80 4 -> 2 Bluegreen (cyan) 120 3 -> 2 Red 180

Bohr model of an atom Excited Ground
Electron Excitation and Emission (at a lower energy)

Creating an Emission Line (Spectral Lines)
Hydrogen Helium Neon Photon Absorption & Emission for a hydrogen atom

Spectral Lines of various elements

h = 6.626 × 10-34 J·sec (Planks Constant) E = h x f
400 nm nm nm nm E = h x f Color Wavelength (nm) h x f = E Violet (6.626 x 10-34) x (1.36 x Hz) (6.626 x 10-34) x (1.45 x Hz) Bluegreen (cyan) (6.626 x 10-34) x (1.62 x Hz) Red (6.626 x 10-34) x (2.19 x Hz) (6.626 x 10-34) x (2.19 x Hz)

Green & Yellow are the only wavelengths that are reflected.
Excited Ground Green & Yellow are the only wavelengths that are reflected. Simulation – mixing colors of light (what people see)

Filters (Only Specific Wavelengths)

Every substance is unique
Excited Ground

Slowing down and changing the direction of light
Degree of Scattering

Slowing down and changing the direction of light
Selective Scattering Degree of Scattering

Why… I need some new/better PPT slides to explain why…
Is the sky blue? Are clouds white/gray? Is the ocean blue/green? Are sunsets red/golden?

Chose One: Include: HOMEWORK: Designing new PowerPoint Slides
blue-sky, white clouds, blue/green oceans, red sunsets Include: 1- How sunlight is a combination of all wavelengths (colors) of light 2- Which EM wavelengths/frequencies are involved (how) 3- How light is absorbed, reflected, scattered, etc. 4- What is occurring at the atomic level (Absorption & Emission) Chapters 27 & 28 – Sections 27.4, 27.5, 28.3, 28.7 – 28.10 On the computer OR hand drawn

Unpolarized Light - waves vibrating in more than one plane
Electric charges vibrate in a variety of directions, thus creating an electromagnetic wave which vibrates in a variety of directions. Unpolarized Light - waves vibrating in more than one plane Polarized light - waves vibrating in a single plane. Polarized Unpolarized Unpolarized Unpolarized

Polarization – process of transforming unpolarized light into polarized light. (Filter)

Using two polarization filters
Polarization axis aligned Polarization axis perpendicular Two Polarization filter - simulation

Polarization by reflection
Glare from the Road Removing the Glare

Question Consider the three pairs of sunglasses below. Identify the pair of glasses is capable of eliminating the glare resulting from sunlight reflecting off the calm waters of a lake? _________ (The polarization axes are shown by the straight lines.) 3-D Glasses

Incident Ray - the ray of light approaching the mirror
Reflected Ray - the ray of light which leaves the mirror The Normal - an imaginary line perpendicular to mirror Angle of Incidence - the angle between the incident ray and the normal Angle of Reflection - the angle between the reflected ray and the normal The law of reflection - when a ray of light reflects off a surface the angle of incidence is equal to the angle of reflection N

Question 1. Consider the diagram above. Which one of the angles (A, B, C, or D) is the angle of incidence? ______ 2. Which one of the angles is the angle of reflection? ______

Question A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection?

Scatters Light in all directions
Reflection off of different types of surfaces Scatters Light in all directions Specular reflection - Reflection off of smooth surfaces such as mirrors or a calm body of water Diffuse reflection - Reflection off of rough surfaces such as clothing, paper, and the asphalt roadway

Rough Surface: Wet vs Dry

What if the Blue floor had a rougher texture?
The law of reflection - the angle of incidence is equal to the angle of reflection (when a ray of light reflects off a surface). Reflection off different types of surfaces What if the Blue floor had a rougher texture?

Reflection of waves --- More than just light
Echoes - when a reflected sound wave reaches the ear more than 0.1 seconds after the original sound wave was heard. > 17 m Reverberations - the prolonging of a sound. The reception of multiple reflections off of walls and ceilings within (less than) 0.1 seconds of each other Since sound waves travel at about 340 m/s at room temperature, it will take approximately 0.1 s for a sound to travel the length of a 17 meter room and back, thus causing a reverberation

Reflection of waves --- More than just light

Reflection of waves --- More than just light
Focusing waves Smooth walls direct sound waves in a specific direction. Rough walls tend to diffuse sound, reflecting it in a variety of directions. This allows a spectator to perceive sounds from every part of the room, making it seem lively and full.

The speed of a wave is determined by the medium
Boundary - When one medium ends, another medium begins; and the behavior of a wave at that boundary is described as its boundary behavior. Change of medium at the boundary The speed of a wave is determined by the medium Slows Down Speeds Up

The boundary behavior of waves - summarized
1- the wave speed is always greatest in the least dense medium 2- the wavelength is always greatest in the least dense medium 3- the frequency of a wave is not altered by crossing a boundary Faster Slower Slower Faster Greater λ Smaller λ Smaller λ Greater λ Frequency does not change Frequency does not change

Question A pulse in a more dense medium is traveling towards the boundary with a less dense medium. The speed of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the speed of the incident pulse coming from the more dense medium. 2. The wavelength of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the wavelength of the incident pulse coming from the more dense medium. 3. The frequency of the pulse in the less dense medium will be _______ (greater than, less than, the same as) the frequency of the incident pulse coming from the more dense medium.

Refraction Does the straw break?

Finish Start Higher Density = Slower wave speed Densest Denser Dense
Minuscule amount of time before release Minuscule amount of time before release Speed of Light Speed of Light Speed of Light Higher Density = Slower wave speed Start Finish Photon Dense Denser Densest Photon Photon

Refraction – Tractor Model

-Caused by a change in speed and wavelength of the waves
Reflection - change in direction of waves when they bounce off a barrier. Refraction change in the direction (bending) of waves as they cross from one medium to another. -Caused by a change in speed and wavelength of the waves Refraction – wave fronts Air Less Dense Faster Glass More Dense Slower Refraction (bending) only occurs at the boundary.

The boundary behavior of waves - summarized
1- the wave speed is always greatest in the least dense medium 2- the wavelength is always greatest in the least dense medium 3- the frequency of a wave is not altered by crossing a boundary More Dense = greater angle Faster Slower Slower Faster Greater λ Smaller λ Smaller λ Greater λ Frequency does not change Frequency does not change Refraction Index simulator - including refraction of individual wavelengths

The amount by which light slows (and therefore bends) in a given material is described by the index of refraction n = c/v Dense Slow Denser Slower Densest Slowest material n Vacuum 1 Crown Glass 1.52 Air 1.0003 Salt 1.54 Water 1.33 Asphalt 1.635 Ethyl Alcohol 1.36 Heavy Flint Glass 1.65 Fused Quartz 1.4585 Diamond 2.42 Whale Oil 1.460 Lead 2.6 More dense More bending Refraction Index, Total Internal Reflection, and Critical Angle Simulation

--Depends upon the Angle of Incidence & the medium density
Total Internal Reflection (TIR) - when the angle of incidence is greater than the critical angle, no refraction occurs. --Depends upon the Angle of Incidence & the medium density Refractive Index Critical Angle The Sparkle of Diamonds – All incoming light can only exit the diamond out of the top of the gem

Total Internal Reflection
Reflection at the Critical Angle (Total Internal Reflection) Critical Angle - The largest angle of incidence for which refraction can still occur. The angle of incidence yields an angle of refraction of 90-degrees. For any angle of incidence greater than the critical angle, light will undergo total internal reflection (TIR). Refraction Critical Angle Total Internal Reflection Critical Angle of Reflection Simulation

Dispersion - the separation of visible light into its different colors
Refraction simulator including individual wave lengths Drop of water

How are rainbows formed?
Prism

Rainbows – Refraction, Dispersion, Reflection
Bending of light Color Separation Direction Change White light Air H2O -Incident white light contains all wavelengths   -Some of the light is reflected -The rest of the light is refracted    -Light splits (dispersion) into component colors    -Reflected at rear of raindrop (TIR – Total internal Reflection)    -Refracted again as it leaves raindrop -Colors are further dispersed

Rainbows – Dependant on the angles (40 - 42°)

Greater angle of incidence = greater angle of refraction

Opening Boundary Diffraction Refraction
Diffraction - a change in direction of waves as they pass through an opening or around an obstacle in their path. (not across a boundary/medium change) Opening Boundary Refraction Diffraction

Diffraction - a change in direction of waves as they pass through an opening or around an obstacle in their path. (not across a boundary/medium change)

Reflection - change in direction of waves when they bounce off a barrier. (Also total interior reflection - TIR) Refraction - change in the direction of waves as they pass from one medium to another. Diffraction - change in direction of waves as they pass through an opening or around an obstacle in their path. Interference

Constructive & Destructive Wave Interference

Constructive interference occurs wherever a thick line meets a thick line or a thin line meets a thin line; this type of interference results in the formation of an antinode. Destructive interference occurs wherever a thick line meets a thin line; this type of interference results in the formation of a node.. `

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