11 - 12 Flashcards
Light emission occurs as a result of these 2 processes
(1) Thermal radiation
(2) Luminescence
What is black body?
An ideal physical body that absorbs all incident of electromagnetic radiation
+> the spectrum of black body will be continues
What is continuous spectrum?
Spectrum that contains all the wavelengths (frequency) (~spectrum of sun)
What is band spectrum?
The spectrum that contains part of continuous spectrum.
It doesn’t contain all the wavelengths (frequency).
It only contains period
What is line spectrum?
The spectrum that contains only 1 special wavelength (or frequency)
What is RADIANT emittance?
The amount of power which is radiated by unit area
What is black body radiation?
Radiation emitted by a body that absorbs all the radiation incident on it
What is an ideal black. body?
The body that has maximal radiant emittance
When do we have maximum absorption?
When we have maximum absorption in a specific wavelength which make our molar extinction coefficient maximum .
State Kirchhoff’s law
At a given temperature, the ratio of the emissive power of a body to its absorptive power is constant and is equal to the emissive power of a black body at the same temperature
-> if an object is absorbing all of the radiation, so absorption coefficient is 1, then radiant emittance is maximum
What is total radiate emittance?
Heat energy proportional to 4th power of specific temperature
State Stefan-Boltzman law
The power of the black body is proportional to 4th power of temperature
State Wien displacement law (and its relationship to blackbody spectrum)
The black-body radiation curve for different temperatures will peak at different wavelengths that are inversely proportional to the temperature.
-> When the temperature of a blackbody radiator increases, the overall radiated energy increases and the peak of the radiation curve moves to shorter wavelengths. When the maximum is evaluated from the Planck radiation formula, the product of the peak wavelength and the temperature is found to be a constant.
3 examples of heat production out of thermal regulation
Metabolic processes
Muscle activity
Secretion
4 ways that heat can be lost from human body
Perspiration
Convection
Radiation
Conduction
What is telethermohgraphy?
Imaging technique which can evaluate the body surface thermal gradients
