The Electromagnetic Spectrum Part 1 Chapter 4 The Electromagnetic Spectrum Part 1

Demonstration Gas spectral tubes: Neon Argon

Visible Light Part of the Electromagnetic Spectrum

All types of electromagnetic energy move in waves. Light and sound move by waves. Light moves at 3 x 108 m/s Sound moves at 340 m/s 1 mile = 1609 m

All types of electromagnetic energy move in waves. Light moves at 3 x 108 m/s Sound moves at 340 m/s Is sound a form of electromagnetic radiation?

Electromagnetic Waves Properties of waves include speed, frequency and wavelength All electromagnetic waves including light travel at a speed of 3 x 108 m/s.

Wavelength () Measured in units of length: m, nm, A º

Frequency () Measured in cycles/second = hertz (Hz)

Visible Light

Why do we want to understand electromagnetic radiation (light)? Well, for one thing, it may someday allow us to become invisible.

Electromagnetic Radiation For all waves  •  = c c = the speed of light = 3.00 x 108 m/s

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light?

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light? 665 nm = 665 x 10-9 m

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light? 665 nm = 665 x 10-9 m c =  • 

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the frequency of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz  = 4.51 x 1014/s or Hz

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength?

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength? 7.25 x 1020 Hz = 7.25 x 1020/s

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength? 7.25 x 1020 Hz = 7.25 x 1020/s c =  • 

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength? 7.25 x 1020 Hz = 7.25 x 1020/s c =  •   = c ÷  = 3.00 x 108 m/s ÷ 7.25 x 1020/s

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength? 7.25 x 1020 Hz = 7.25 x 1020/s c =  •   = c ÷  = 3.00 x 108 m/s ÷ 7.25 x 1020/s  = 4.137931 x 10-13 m

An x-ray has a frequency of 7.25 x 1020 Hz. What is the wavelength? 7.25 x 1020 Hz = 7.25 x 1020/s c =  •   = c ÷  = 3.00 x 108 m/s ÷ 7.25 x 1020/s  = 4.137931 x 10-13 m  = 4.14 x 10-13 m

Energy of Electromagnetic Radiation For all waves: E = h •  h = 6.63 x 10-34 J • s or J/Hz

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the energy of this light?

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the energy of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz  = 4.51 x 1014/s or Hz

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the energy of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz  = 4.51 x 1014/s or Hz E = h •  = (6.63 x 10-34 J • s)(4.51 x 1014/s)

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the energy of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz  = 4.51 x 1014/s or Hz E = h •  = (6.63 x 10-34 J • s)(4.51 x 1014/s) E = 2.99013 x 10-19 J

A photon of red light has a wavelength of 665 nm A photon of red light has a wavelength of 665 nm. What is the energy of this light? 665 nm = 665 x 10-9 m c =  •   = c ÷  = 3.00 x 108 m/s ÷ 665 x 10-9 m  = 4.511278 x 1014/s or Hz  = 4.51 x 1014/s or Hz E = h •  = (6.63 x 10-34 J • s)(4.51 x 1014/s) E = 2.99013 x 10-19 J = 2.99 x 10-19 J

An x-ray has a frequency of 7.25 x 1020 Hz. What is its energy?

An x-ray has a frequency of 7.25 x 1020 Hz. What is it’s energy? E = h •  = (6.63 x 10-34 J/Hz)(7.25 x 1020Hz)

An x-ray has a frequency of 7.25 x 1020 Hz. What is it’s energy? E = h •  = (6.63 x 10-34 J/Hz)(7.25 x 1020Hz) E = 4.80675 x 10-13 J

An x-ray has a frequency of 7.25 x 1020 Hz. What is it’s energy? E = h •  = (6.63 x 10-34 J/Hz)(7.25 x 1020Hz) E = 4.80675 x 10-13 J E = 4.81 x 10-13 J

wavelength, frequency and energy Red Light  = 665 x 10-9 m  = 4.51 x 1014 Hz E = 2.99 x 10-19 J  = 4.14 x 10-13 m  = 7.25 x 1020 Hz E = 4.81 x 10-13 J X-ray

Wavelength, frequency and energy Wavelength and frequency have an inverse relationship. Energy and frequency have a direct relationship. Electromagnetic radiation with a shorter wavelength will have a higher frequency and higher energy. Electromagnetic radiation with a longer wavelength will have a lower frequency and lower energy.

The Electromagnetic Spectrum Part 2 Chapter 4 The Electromagnetic Spectrum Part 2

Radio waves Includes FM, AM, and TV waves Used in many devices such as remote control items, cell phones, wireless devices, etc.

Radio Astronomy

Microwaves First used in radar, now used in communication (wireless local internet networks), and consumer use (microwave ovens). medical applications in cancer treatment (destroy tumors by heating them). “Active Denial System” – the “Pain Ray”

Microwaves The Active Denial System (ADS) is a non-lethal weapon developed by the U.S. military. It is a micro-wave transmitter used for crowd control. Informally, the weapon is also called the pain ray. The ADS works by directing microwave radiation toward the subjects. The waves excite water molecules in the epidermis to around 130 °F (55 °C), causing an intensely painful sensation of extreme heat. While not actually burning the skin, the burning sensation is similar to that of a light bulb being pressed against the skin. Wireless LAN (Local Access Network) protocols, such as Bluetooth also use microwaves.

The Cloak of Invisibility Physicists in Texas have developed a method to make objects "invisible" within a limited range of light waves. It's not Harry Potter's invisibility cloak just yet, but scientists say it has a lot of potential.

The Cloak of Invisibility Light and invisibility We see things because light reflects off of them and hits our eyes. Or radar (microwaves) bounce off of them and hit a detection device. Light has properties that can be manipulated, which is how objects can be rendered invisible. It can be reflected away, for example. Illusionists can use mirrors to make an object disappear.

Light also refracts -- or bends -- when it passes through an object such as a prism or raindrops, resulting in the colors we see in a rainbow.

Previous attempts at achieving invisibility have involved refracting (bending) or reflecting light around the object so as to make it appear to vanish. The invisibility cloak takes a new approach. It attempts to disturb the light beams so as to neutralize them.

The cloak's material The cloak is made by combining copper tape with polycarbonate, a material commonly used in DVD's and CDs. The resulting cloak has a tiny pattern that neutralizes the waves bouncing off of it.

For it to work, the material's pattern has to be roughly the size of the wavelength of light to be canceled out. Unfortunately that only allows it to work on a limited range of wavelengths.

Current technology allows the cloak to work with only microwaves but scientists say the principle behind the cloak can also be used for visible light.

So far it has only been able to hide objects from the human eye that are so tiny that we can't see them anyway. However, scientists believe that this could "pave the way" for larger objects to be rendered “invisible”.

Infrared Missile guidance systems use the emission from a target of electromagnetic radiation in the infrared part of the spectrum to track it. Infrared radiation can be used as a heating source. For example it is used in infrared saunas, and also to remove ice from the wings of aircraft (de-icing). Infrared thermomedic therapy uses thermal technology to provide compressive support and healing warmth to assist symptom control for arthritis, injury & pain. IR data transmission is also employed in short-range communication among computer peripherals and personal digital assistants (PDA’s) Weather satellites produce infrared images to aid in the prediction of weather.

Infrared Waves Infrared radiation is popularly known as "heat“ Used in heat lamps de-icing systems thermomedic therapy.

Infrared Waves Missile guidance systems, short range communication systems

Infrared Radiation can be detected with special devices such as night goggles

Weather satellites track weather systems using infrared.

Visible Light The portion of the electromagnetic spectrum that human eyes can detect ROY G BIV (red, orange, yellow, green, blue, indigo, violet). Why can we only see the visible light portion of the spectrum?

Visible Light The Sun is the dominant source for visible-light waves our eyes receive. Our Sun produces more yellow light than any other color because its surface temperature is 5,500°C. If the Sun's surface were cooler—say 3,000°C—it would look reddish, like the star Betelgeuse. If the Sun were hotter—say, 12,000°C—it would look blue, like the star Rigel.

Why do the colors of the stars correspond to their temperatures?

Homework Chapter 4: Worksheet 1 (due tomorrow) Chapter 4: Worksheet 2 (due in two days)