HONORS

Electromagnetic Waves Remember… Electromagnetic waves: electric and magnetic waves released by a vibrating electric charge, capable of transferring energy through a vacuum. Do not need a medium to travel through. Instead of transferring energy from particle to particle like mechanical waves, they transfer energy between electric and magnetic fields, which can exist with or without matter. All electromagnetic waves travel at a speed of 300,000,000 m/s in a vacuum. They slow as they travel through matter.

Waves vs. Particles Waves: a disturbance that can carry energy. Remember… Waves: a disturbance that can carry energy. Particles: pieces of matter. Electromagnetic waves can behave as waves and as particles, called photons. Photon: massless bundle of energy. I like this kind of artsy photo that gives us an image of what an electromagnetic wave could look like (if we could see it) as they send messages out of our phones.

Electromagnetic Spectrum Electromagnetic waves give off energy in the form of electromagnetic radiation. There is a broad range in the different types of EM radiation. Electromagnetic spectrum: the entire range of frequencies of electromagnetic radiation.

Electromagnetic Spectrum ROYGBIV Longer wavelength Lower frequency Lower energy Shorter wavelength Higher frequency Higher energy

Electromagnetic Spectrum Radio waves: emitted by radio stations, MRI’s, RADAR, Wi-Fi, TV, and cell phones. Longest wavelength with the lowest frequency. Radio stations: convert radio waves into sound waves so you can hear your music! MRI = Magnetic Resonance Imaging: take pictures inside the body. RADAR = tracking movement of objects/devices like airplanes or cars.

Electromagnetic Spectrum Microwaves: used for cooking, Doppler radar, and GPS. Doppler radar is used for weather forecasting.

Electromagnetic Spectrum Infrared waves: used in night vision goggles, remote controls, and infrared photography.

Electromagnetic Spectrum Visible Light waves: the only electromagnetic waves we can see; given off by the sun and light bulbs. Different colors of light have different wavelengths. ROYGBIV – red is the longest and violet is the shortest.

Electromagnetic Spectrum Ultraviolet waves: given off by the sun; used in light bulbs, to kill bacteria, and by the human body to make vitamin D.

Electromagnetic Spectrum X-Rays: used to take pictures of bones to check for breaks and fractures, also used in CAT scans. Small enough to penetrate skin cells. Overexposure can cause cancer. CAT scans: make 3-D images out of lots of 2-D x-ray images.

Electromagnetic Spectrum Gamma Rays: used to kill cancer cells, sterilize medical equipment, and in radioactive tracers. Smallest wavelength with the highest frequencies. After this overview of the EMS, I like to go into some additional topics on waves just for my honors students, as you will see in the remaining slides. Feel free to use with your CP students too if you want to go into more depth!

Doppler Effect Doppler Effect: change in frequency (and thus pitch) due to a moving wave source. Frequency increases as source moves towards an observer and decreases as the source moves away from the observer. Source of wave must be moving with respect to the observer. Used by astronomers to understand moving stars. Most often experienced in your life with sound waves.

Doppler Effect Shorter 𝞴 Higher 𝒇 Higher pitch Longer 𝞴 Lower 𝒇 As the fire truck moves towards the kids: Waves are more compressed so… Shorter 𝞴 Higher 𝒇 Higher pitch As the fire truck moves away from the kids: Waves are more spread apart so… Longer 𝞴 Lower 𝒇 Lower pitch

Seeing When light hits an object, the object absorbs most of the light and reflects the rest. Whatever color is reflected hits your retina. You see the reflected color. Two parts of retina that help you see: Rods: work at low levels of light; used mainly at night. Cones: work at bright light levels; allow us to see color. Fun Fact: Colorblindness occurs when one or more sets of cones fail to work properly.

Seeing Convex Lenses (aka Converging Lens) Lenses are used to redirect light waves and correct vision. There are two kinds. Convex Lenses (aka Converging Lens) Thicker at middle than ends. Bend light inwards to a single focal point. Used to correct far-sightedness and for magnification. Connect back to behaviors of waves – this is REFRACTION! Ex. Reading glasses, magnifying glass, rearview mirror.

Seeing Concave Lenses (aka Diverging Lens) Thicker at the ends. Lenses are used to redirect light waves and correct vision. There are two kinds. Concave Lenses (aka Diverging Lens) Thicker at the ends. Bend all light outwards. Used for correcting near-sightedness Ex. Projector, makeup mirror, dentist mirror. Connect back to behaviors of waves – this is REFRACTION!