Download WAVES: disturbance that transfers energy from place to place

Unit 11-­‐2 Notes WAVES: disturbance that transfers energy from place to place. Waves are matter and energy interacting. Mechanical waves require a medium to transfer energy (Mechanical=Medium) medium -­‐ solid, liquid or gas through which a wave travels . Electromagnetic waves do not require a medium. MECHANICAL WAVES: 3 types = Transverse waves move the medium at right angles or perpendicular to the direction the wave is travelling. Longitudinal waves move the medium in the same direction the wave travels. Surface waves are a combination of transverse and longitudinal waves, (more in a circular rotation) MECHANICAL TRANSVERSE WAVES Waves start at resting position. The crest is the highest point. The trough is the lowest point. WAVELENGTH: distance between two waves, measures the distance between two crests or two troughs. (measured in NANOMETERS) The shorter the wavelength = the more energy. AMPLITUDE = height of a wave measured from its resting position. The higher the amplitude = the MORE energy FREQUENCY = number of wave crests per second. (measured-­‐ Hertz, abbreviated: Hz) A frequency of one cycle per second is one Hertz,. Frequency and wavelength determines how much energy a wave has. As frequency increases (more waves per second), the wavelength (length of wave) decreases. The smaller the wavelength, the higher its frequency, and the more energy a wave has. Example: Water ripples, jump rope MECHANICAL LONGITUDINAL WAVES (compressional waves) The wave gets pushed back and forth. Compression: the parts of the wave are close together. Rarefaction: parts of the wave that are spread out. The compressions and rarefactions of a longitudinal wave correspond to the crests and troughs of transverse waves. The more crowded a compression is, the higher it’s amplitude. Examples: sound, pressure and seismic (earthquake) waves. ELECTROMAGNETIC (EM) WAVES: travel at the speed of light (300,000 km/s), and DO NOT require a medium to travel. Visible light is just one part of the EM spectrum. EM waves help us see components of the universe that are normally invisible to our eyes. All objects in our Universe emit, reflect, and/or absorb electromagnetic radiation, and scientists use EM waves to study an object’s composition, temperature, density, age, absolute magnitude (true brightness), luminosity (amount of light energy), apparent magnitude (light as seen from Earth), distance, etc. Radio waves & Microwaves: long wavelengths (lower energy amounts) (Cold regions of space emit low energy waves) Visible/Optical light: observable colors (ROYGBIV colors) such as red, green, blue. A spectroscope is used to observe light by splitting the light into different color wavelengths WE CAN SEE (WITH OUR EYES) VISIBLE/OPTICAL, BUT NOTICE IT’S A SMALL PORTION OF THE EM SPECTRUM! Ultraviolet (UV) rays: come from a star (like our Sun) and are shorter wavelength than visible, radio, and microwaves; therefore UV rays give off more energy. UV rays are beneficial because the energy helps our bodies create vitamin D. Too much UV radiation can damage cells and cause sunburns/cancer. (Used to study young–medium stars) Infrared rays -­‐ longer than visible light and cannot be seen, but felt as heat. (Used to study star-­‐forming regions) X-­‐rays have very short wavelengths and therefore have very high frequencies and lots of energy. Gamma rays have shortest wavelengths and highest frequencies of all the electromagnetic waves; therefore have the highest amount of energy that can penetrate matter the most. If we are exposed to gamma rays, its high energy can cause serious illness. Doctors can use targeted gamma to possibly kill cancer cells. Some radioactive/nuclear reactions produce gamma rays, as well as stars. EM waves that CANNOT penetrate our atmosphere are microwaves, ultraviolet, X-­‐ray, and gamma ray. EM waves that CAN penetrate are radio, visible, and a few infrared waves.