Properties and Characteristics EM NOTES Properties and Characteristics

What do we know about EM waves in general? They are ALL Energy—Radiation! Non-mechanical Transverse waves They do not need a medium—travel in space!! Have crests/troughs They all travel at the speed of light (300,000 km/sec) in space! Fastest: Space…air…water…solid: slowest Most are not visible by the human eye!

How are EM waves Different?

How are EM waves Different? They have different Frequencies Wavelengths Amounts of energy These characteristics impact some of their properties and behavior!

ROY G. BIV One EM Example: The EM wave we can detect (see) Visible Light The EM wave we can detect (see) It is WHITE = blend of all colors ROY G. BIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet) Different due to wavelength and frequency

Wave Behavior EM waves behave a certain way when they hit a material. They may possibly… Reflect—bounce off Absorb – held within = heat Transmit- travel through

Reflection Waves bounce (reflect) off of a surface at the same angle that they hit the surface at. Mirror

Reflection Examples: MIRRORS!!! Four eyed mutant bipeds

Reflection Sound can be reflected also = Echo Other real-life examples… A submarine periscope Games dealing with angles! Ping pong, basketball, pool Sound can be reflected also = Echo

Absorption & Reflection Why do we see certain colors? Different frequencies of light are “absorbed” or “reflected” What we see = reflected to our eyes

Absorption & Reflection Red Truck is red because… Truck absorbs all light waves except red red is reflected back to our eyes Do you wear a white or black shirt in the summer? If all light is absorbed = BLACK = Hotter If all light is reflected = WHITE = Cooler

Absorption & Reflection Black clothes absorb more light energy = HEAT!!! Avoid black in summers Wear black in winters

Waves Transmitted Waves travel through an object/material Not reflected or absorbed What two things will determine if a wave transmits through? The waves energy and The medium When they travel through they may… 1. Refract OR 2. Disperse or Diffract

Refraction waves change speeds as they move through different mediums. Changing speeds causes Waves To Bend! Wave going in (Water) Wave refracted

Refraction Example: Where is the fish actually at if you are fishing using the diagram? WHY?

Refraction Example: Where is the fish actually at if you are fishing using the diagram? WHY? The fish is actually further than what the man will see. Actual fish

Dispersion / Diffraction When white light passes through a prism or slit it bends causing the colors to separate so you can see them. What causes a rainbow? raindrops cause the light to disperse