afocal system

Examples of afocal system in the following topics:

• Combinations of Lenses

  • If two thin lenses are separated in air by some distance d (where d is smaller than the focal length of the first lens), the focal length for the combined system is given by
  • This type of system is called an afocal system, since it produces no net convergence or divergence of the beam.
  • Although the system does not alter the divergence of a collimated beam, it does alter the width of the beam.
  • (b) Multiple-lens systems, such as this achromatic doublet, can partially correct chromatic aberrations, but they may require lenses of different materials and add to the expense of optical systems such as cameras.

• The First Law

  • The 1st law of thermodynamics states that internal energy change of a system equals net heat transfer minus net work done by the system.
  • It is usually formulated by stating that the change in the internal energy of a closed system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings.
  • Here ΔU is the change in internal energy U of the system, Q is the net heat transferred into the system, and W is the net work done by the system.
  • So positive Q adds energy to the system and positive W takes energy from the system.
  • W is the total work done on and by the system.

• Work

  • Work performed by a closed system is the energy transferred to another system that is measured by mechanical constraints on the system.
  • In thermodynamics, work performed by a closed system is the energy transferred to another system that is measured by mechanical constraints on the system .
  • For closed systems, energy changes in a system other than as work transfer are as heat.
  • Heat transfer into a system, such as when the Sun warms the air in a bicycle tire, can increase its temperature, and so can work done on the system, as when the bicyclist pumps air into the tire.
  • However, both can change the internal energy of a system.

• Internal Energy

  • The internal energy of a system is the sum of all kinetic and potential energy in a system.
  • However, a system does contain a quantifiable amount of energy called the internal energy of a system.
  • The equation describing the total internal energy of a system is then:
  • Q is heat added to a system and Wmech is the mechanical work performed by the surroundings due to pressure or volume changes in the system.
  • We can calculate a small change in internal energy of the system by considering the infinitesimal amount of heat δQ added to the system minus the infinitesimal amount of work δW done by the system:

• Prefixes and Other Systems of Units

  • Prefixes in varying multiples of 10 are a feature of all forms of the metric system, with many dating back to the system's introduction in the 1790s.
  • The SI Unit system, or the metric system, is used by the majority of countries in the world, and is the standard system agreed upon by scientists and mathematicians.
  • Colloquially, however, other systems of units are used in many countries.
  • The system for measuring length using the United States customary system is based on the inch, foot, yard, and mile.
  • The twenty prefixes officially specified by the International System of Units

• The Zeroth Law of Thermodynamics

  • The Zeroth Law of Thermodynamics states that systems in thermal equilibrium are at the same temperature.
  • Let A, B, and C be three systems.
  • The double arrow represents thermal equilibrium between systems.
  • If systems A and C are in equilibrium, and systems A and B are in equilibrium, then systems B and C are in equilibrium.
  • The systems A, B, and C are at the same temperature.

• A Review of the Zeroth Law

  • Zeroth law justifies the use of thermodynamic temperature, defined as the shared temperature of three designated systems at equilibrium.
  • The Zeroth Law of Thermodynamics states: If two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.
  • Two systems are in thermal equilibrium if they could transfer heat between each other, but don't.
  • Indeed, experiments have shown that if two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system C, then A is also in thermal equilibrium with C.
  • Zeroth law justifies the use of thermodynamic temperature : the common "label" that the three systems in the definition above share is defined as the temperature of the systems.

• Internal vs. External Forces

  • Let's first list all the forces present in the system.
  • How should we define our system?
  • Therefore, our system consists of two pucks (and nothing else).
  • Total momentum of the system (or Cradle) is conserved.
  • (neglecting frictional loss in the system. )

• Pressure in the Body

  • Pressure plays an essential role in various critical bodily systems that are necessary for survival.
  • One such critical bodily system which relies on pressure for functionality is the circulatory system, which is an example of a closed fluid system under pressure.
  • Blood can be regarded as a viscous liquid contained within the circulatory system that travels throughout this closed system as a result of pressure and pressure differences within the circulatory system.
  • As the volume of blood within the circulatory system is confined to the veins, arteries, and capillaries there is a pressure within this closed system.
  • Explain role played by pressure in the circulatory and respiratory systems

• Conservation of Mechanical Energy

  • Conservation of mechanical energy states that the mechanical energy of an isolated system remains constant without friction.
  • Conservation of mechanical energy states that the mechanical energy of an isolated system remains constant in time, as long as the system is free of all frictional forces.
  • An example of a such a system is shown in .
  • Though energy cannot be created nor destroyed in an isolated system, it can be internally converted to any other form of energy.
  • The total kinetic plus potential energy of a system is defined to be its mechanical energy (KE+PE).