 Welcome to the temperature emissivity of non-black bodies. Please note, before viewing this lesson, please review the learning object ratio pyrometers. Radiation pyrometer temperature measuring devices operate on the assumption that the total energy emitted by a body or physical object is the result of its temperature. However, energy is also radiated by being reflected and transmitted by passing light as a fiber optic strand does. These two types of energy are not affected by temperature. The target object radiates emitted e reflected r and transmitted t energy to the measurement detector. The total energy radiated from an object is the sum of emitted energy e reflected energy r and transmitted energy t. It is represented by the formula radiated energy equals e plus r plus t. If an object only radiated emitted energy resulting from its temperature alone, it would be called a black body and its formula would be radiated energy e equals 1 r equals 0 and t equals 0. For a non-black body object, the value of e would also be 1.0 but its r and t values would be greater than 0 because there is reflected and transmitted energy radiated. To account for the reflected and transmitted energy from an object, a term called emissivity must be considered when making measurements. Emissivity is the ratio of total energy radiated by an object to the emitted energy of a black body made of the same material at the same temperature. Based on this definition, the emissivity values are black body equals 1.0, non-black body equals 0.1 to 0.9. Emissivity values are used to compensate for the reflected and the transmitted energy received by the radiation pyrometer when making temperature measurements. Suppose the temperature of the non-black body carbon is 76 degrees Fahrenheit. Since it radiates more energy than a black body at the same temperature because the carbon radiates reflected and transmitted energy, the radiation pyrometer will measure a higher reading than 76 degrees. By incorporating the r and t values that are greater than 0 into the radiated energy formula, the emissivity value which becomes less than 1 is determined. For non-black body carbon, the emissivity value is 0.8. This number is used to compensate for the unwanted reflected and transmitted energy received by the pyrometer that adds to the actual temperature emitted energy. By setting an emissivity adjustment knob to 0.8 on the radiation pyrometer, the pyrometer will electronically calculate the proper temperature emitted by the object. The emissivity setting required for most materials is obtained from the table's electronic and paper data that were developed in a research laboratory. The tables were created by drilling holes into various materials to form black bodies. Only emitted energy comes from the holes, not reflected or transmitted energy. Radiated energy is then measured from non-black bodies made of the same materials. The radiated energy of black bodies and non-black bodies measured in the laboratory is then used to calculate the emissivity of each material and entered into the table. Now let's check your understanding. Feel free to pause the video if you need more time to figure out the answer. Radiated energy from an object comes from emitted, reflected, and transmitted energy. Which type of radiated energy is the result of an object's temperature? The answer is A, emitted energy. The radiated energy of a black body is 1. To compensate for the effect of reflected and transmitted energies, the temperature of an object can be determined by using an emissivity calculation. The emissivity value of a non-black body is less than 1. Congratulations, you have completed this activity, with the future emissivity of non-black bodies.