Light Big Idea: Electromagnetic Radiation, which includes light, is a form of radiant energy possessing properties of both waves and zero-mass particles called photons. Photons vary in their energy, which causes them to vary in their frequencies and wavelengths as well. EM radiation can be bent (refracted) or reflected by certain materials, allowing us to manipulate how it travels and what kinds of images it produces. Topic 7.1: Light basics and the EM spectrum Topic 7.2: Refraction Topic 7.3: Reflection and Polarization Topic 7.4: Diffraction and Wave-Particle Duality

Learning Goal: You will be able to describe the relationships between, wavelength, frequency, speed, and energy. Success Criteria: You will know you have met the learning goal when you can truthfully say: I can calculate the speed, wavelength, frequency, or energy of a photon of light. I can describe the relative energies of the different regions of the electromagnetic spectrum. Image(s) from Bing Images

Success Criteria 1: I can calculate the speed, wavelength, frequency, or energy of a photon of light. You know from previous science classes that the colors of light vary as a function of frequency. So what determines which frequencies of radiation an object will emit? Similar to the way that objects have a resonant frequency depending on how fast sound travels through them and how large they are, the electron configuration in an atom or molecule has a sort of resonant frequency that determines which frequencies of light it will produce. (There are many differences between the classical concept of resonance and the quantum mechanical reasons for why light of a certain frequencies is produced. It’s an analogy that gets relatively close to explaining what is happening, though, so we’ll use it. Just be aware that the truth is a bit more complicated.) Image(s) from Bing Images

c = the speed of light in a vacuum = 3.00 x 108 m/s. Success Criteria 1: I can calculate the speed, wavelength, frequency, or energy of a photon of light. When an electron emits a photon, it travels at 299,792, 458 m/s (often rounded to 300,000,000 m/s). That’s fast enough to get from Seattle to New York in about 1/60 of a second. As we’ll see later in the unit, light slows down a bit when it travels through materials such as glass or water, but not enough for us to notice. This value is given the letter c: c = the speed of light in a vacuum = 3.00 x 108 m/s. Using this speed and the wave equation we learned in the previous unit (v = λf), we can relate the speed, wavelength, and frequency of light. Physicists and chemists have realized that the energy of light is directly related to its frequency. The energy of one photon of light can be calculated using this equation: E = hf E = energy in joules (J), h = Planck constant (6.6261 x 10-34 Js, f = frequency of light in Hertz (Hz). Image(s) from Bing Images

To summarize these two equations: Success Criteria 1: I can calculate the speed, wavelength, frequency, or energy of a photon of light. To summarize these two equations: Task 7.1.1 (12 points): Find the wavelength, frequency, energy, and type of radiation. Additional prefixes: Relating speed, wavelength, and frequency Relating frequency and energy (Planck-Einstein relation) Speed of light in a vacuum Planck constant c = λf E = hf 3.00 x 108 m/s 6.6261 x 10-34 Js Wavelength (m) Frequency (Hz) Energy (J) Type of rad. a) 460 nm b) 150 μm c) 3.62 x1014 Hz d) 6.72 x 1018 Hz e) 7.02 x 10-19 J f) 2.26 x 10-13 J Giga (G) Tera (T) Peta (P) Exa (E) Billion = 109 Trillion = 1012 Quadrillion = 1015 Quintillion = 1018 Image(s) from Bing Images

Success Criteria 1: I can calculate the speed, wavelength, frequency, or energy of a photon of light. Task 7.1.2 (5 points): Answer these questions: An experiment measures the wavelength of green light to be about 580 nm. What is the energy of a photon of this type of light? Our eyes are sensitive to light of wavelengths between about 380 nm and 750 nm. If a type of EM radiation is reported as having a frequency of 93 terahertz, would our eyes be able to see it? Some guy tells you that the government reads your thoughts using 60 nm radio waves. Does this wavelength correspond to the radio wave region of the EM spectrum. Atoms are ionized when photons above a certain energy collide with electrons. Would an electron that requires 7.8 x 10-18 J of energy to be ejected be ejected if it absorbs a photon of wavelength 22 nm? What region of the EM spectrum is the radiation from part d?

Success Criteria 2: I can describe the relative energies of the different regions of the electromagnetic spectrum. Our phones send and receive signals using microwaves. We listed to the radio using radio waves. We’ll all had an X-ray and some point in our lives, which uses high-energy radiation to see inside our bodies. All of these types of radiation are part of the electromagnetic spectrum, or EM spectrum.

Success Criteria 2: I can describe the relative energies of the different regions of the electromagnetic spectrum. Task 7.1.3:(10 points): As a group, sign up with Mr. Czajka to do one of the seven types of electromagnetic radiation. Create a one page poster that answers the following questions. We will present them to the class and take notes on them, so your poster should include the following elements: Neat and large writing. Illustrations to help the audience visualize the concepts you are describing. For your group’s type of radiation, answer these questions: What range of wavelengths and frequencies does it include? What temperature object will emit it as blackbody radiation? How do humans produce it with technology? What are at least three uses we have for it?

Task 7.1.4 (4 points): Write at least 8 things you learned in this topic (1/2 point each). If you do this in your notebook, please do it in list form rather than paragraph form. Image(s) from Bing Images