Absorption & Emission of Light Stimulated Absorption & Emission‚ Spontaneous Emission E2 Incident radiation hν hν Emitted & transmitted radiation E1 Resonance condition E2-E1=hν • Rate of stimulated emission is: −dN1/dt = N1B1->2 ρ(ν) • Rate of absorption is the sum of the rated due to stimulated emission and spontaneous emission: −dN2/dt = N2B2->1 ρ(ν) + N2A2->1 where B1->2 is the Einstein transition probability for induced absorption‚ B2->1 is the Einstein transition probability
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NS 10.5 (pg 1 of 2) Heating and Cooling Curves What happens when we heat a sample of ice that is initially at -15°C? The addition of heat causes the temperature of the ice to increase. As long as the temperature is below 0°C‚ the sample remains frozen. When the temperature reaches 0°C (the melting point of water)‚ the ice begins to melt. Because melting is an endothermic process‚ the heat we add at 0°C is used to convert ice to water and the temperature remains constant until all the ice
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1. Characteristic Loads-Characteristics‚ Importance‚ Applications Actions By E.C. An action (F) is a force (load) applied to the structure (direct action ) or an imposed deformation ( indirect action ) ex. Temperature effects. Actions are classified: a) by variation in time permanent actions G ( self-weight of structure). b) by their spatial variations: fixed actions ( self weight ) variable actions Q wind loads/snow. free actions which results in different actions accidental actions
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Intermolecular forces exist between independent particles‚ such as atoms‚ ions‚ or molecules. They can be forces of either attraction or repulsion. The amount of charge‚ how it is distributed‚ and the length of time that a charge distribution exists can affect the strength of intermolecular forces. And despite having variable force strengths‚ all intermolecular forces are considered weak compared to chemical bonds‚ or intramolecular forces. Chemical bonds are not only stronger; they are also more
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Give some example of everyday vibrating object. which exhibit SHM‚ at least approximately? 1. The pendulum on an old clock. 2. A guitar string after it gets plucked 3. The vibrations of the little quartz crystal in a digital watch. 2. toys called Newton’s cradle 3. the motion of a piston in an engine and 4. the vibrations of the atoms in a solid. 5. A micromass particle of light exhibits SHM.The Reason is that it oscillates without any mass changes during its motion. Is the acceleration
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The piezoresistive effect is given by (1 2 ) R R (1) where is the resistivity of the piezoresistor‚ depends on the doping concentration of the piezoresistors‚ ν is the Poisson’s ratio and is the mechanical strain induced in the diaphragm. The first part of the left hand side of equation 1 describes the piezoresistive effect and the second part defines the geometric effect. For piezoresistive materials like polysilicon‚ the piezoresistive effect dominates over geometric effect
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A mathematical model which is investigated the thermal and physical behavior of a dish/Stirling system is presented‚ then the system was designed‚ analyzed and optimized. There are many types of heat losses in the dish/Stirling system‚ such as convection and conduction heat losses and radiation heat losses by emission in the cavity receiver and reflection heat loss of solar energy in the parabolic dish. There are also internal and external conduction heat losses‚ energy dissipation by pressure drops
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Optical Properties of Quasicrystals: Negative Refraction Quasicrystals‚ or crystals that display the unusual property of non-periodicity (while remaining ordered)‚ were discovered in the 1980s by Dan Shechtman. A highly controversial topic‚ Shechtman did not produce a paper describing them for over two years after their discovery. However‚ within the past 30 years‚ the scientific community has come to accept them‚ reproduce them for study‚ and even award Dan Shechtman with a Nobel Prize for their
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EXERCISE 8 - Rotational Dynamics‚ Equilibrium of rigid body 1. If the torque required to loosen a nut that is holding a flat tire in place on a car has a magnitude of 40.0 N m‚ what minimum force must be exerted by the mechanic at the end of a 30.0-cm lug wrench to accomplish the task? 133 N 2. A steel band exerts a horizontal force of 80.0 N on a tooth at point B in Figure 1. What is the torque on the root of the tooth about point A? 0.64 Nm 3. Calculate the net torque (magnitude and
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CIEG-306 Fluid Mechanics Laboratory 2. Stability of a Floating Body Objective The objectives of this experiment are: 1. to measure the angle of inclination at which an eccentrically loaded body floats‚ 2. to observe the circumstances under which a floating body is unstable‚ and 3. to compare the observed results with theoretical predictions. Apparatus The apparatus consists of an open plastic box (‘barge’) which floats in water and carries a mast (Figure 1). A plumb-bob suspended from the
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