Energy • • • • Ability to do work Many different forms Conservation of energy (Law) Transformed: example: – Radiant to Thermal – Kinetic to Thermal (friction) Absolute Zero • As low as you can go • -273 degrees Celsius • All particles stop moving The Electromagnetic Spectrum Light (medium wavelength) made up of several color components Infrared (long wavelength) eg: Heat Escaping from People UV (short wavelength) causes sunburn and skin cancer X-rays (very short wavelength) Insolation • SOLAR RADIATION (radiation coming from the sun) – Includes different types of radiation (UV/Infrared) – Visible light makes up the majority of this radiation Transmission, Absorption, and Scattering • Transmission – Wave passes through matter • Scattering • Absorption – Wave and energy are absorbed – Waves absorbed and reemitted • Diffuse scattering • Reflection Refraction Scattering • Scattering is the redirection (in all directions) of light by small particles and gas molecules in the atmosphere; The result is more light rays with weaker intensity. Diffuse Scattering of Sunlight Scattering of Light through Reflection Absorption of Sunlight by Asphalt 17.2 Heating the Atmosphere Conduction • Conduction is the transfer of heat through matter by molecular activity; Energy is transferred through collisions from one molecule to another. Convection • Convection is the transfer of heat by the movement of a mass or substance; It can take place only in liquids and gases. Radiation • Radiation is the transfer of energy (heat) through space by electromagnetic waves. Temperature • Temperature is a measure of the average kinetic energy of individual atoms or molecules in a substance. Heat • Heat is thermal energy transferred from one object to another. (Calories) Joules • Unit of Energy • Calories is used in the US • Joules is metric unit SPECIFIC HEAT • The amount of energy needed to heat 1 gram of a substance by one degree celsius Heat is the energy transferred from one object to another because of a difference in their temperatures. Reflection • Reflection is the process whereby light bounces back from an object at the same angle at which is encounters a surface and with the same intensity. Three mechanisms of energy transfer as heat are conduction, convection, and radiation. Unlike conduction and convection, which need material to travel through, radiant energy can travel through the vacuum of space. When radiation strikes an object, there usually are three different results. 1. Some energy is absorbed by the object. 2. Substances such as water and air are transparent to certain wavelengths of radiation. 3. Some radiation may bounce off the object without being absorbed or transmitted. How the atmosphere is heated: • All objects, at any temperature, emit radiant energy. • Hotter objects radiate more total energy per unit area than colder objects. • The hottest radiating bodies produce the shortest wavelengths of maximum radiation. • Objects that are good absorbers of radiation are good emitters as well. Greenhouse Effect • Greenhouse effect is the heating of Earth’s surface and atmosphere from solar radiation being absorbed and emitted by the atmosphere, mainly by water vapor and carbon dioxide.