User:Agaba isaac Kenyatta University

Power in optics
In optics, or radiometry, the term power sometimes refers to radiant flux, the average rate of energy transport by electromagnetic radiation, measured in watts. The term "power" is also, however, used to express the ability of a lens or other optical device to focus light. It is measured in dioptres (inverse metres), and equals the inverse of the focal length of the optical device. A similar relationship is obtained for rotating systems. MA=FB FA=vB vB If mechanical has no losses then the fact that the system



P_\mathrm{avg} = \frac{\Delta W}{\Delta t}\,. $$ It is the average amount of work done or energy converted per unit of time. The average power is often simply called "power" when the context makes it clear.

The instantaneous power is then the limiting value of the average power as the time interval Δt approaches zero.

P = \lim _{\Delta t\rightarrow 0} P_\mathrm{avg} = \lim _{\Delta t\rightarrow 0} \frac{\Delta W}{\Delta t} = \frac{dW}{dt}\,. $$

In the case of constant power P, the amount of work performed during a period of duration T is given by:

W = PT\,. $$ Types of Networks

Basically, there are two main classes of networks - Client/Server and Peer-to-Peer (P2P). Earlier networks were client/server but peer-to-peer has gained popularity.

Client/Server Network In a client/server network, the client computer requests information from the server computer which stores the data on the network. The server PC is always ready to dispense requested data from the client computers on the network.

The greatest example of a client/server network is illustrated when we are surfing the Internet. Your PC is then referred to as the client PC when you request a Web site from a server PC on the Internet. The server PC directs the Web site's contents to your web browser for viewing.

Peer-to-Peer Network Peer-to-peer computer networking does not require separate client and server PCs. Each node in a peer-to-peer network can function as client or server.

These are special networks that operate with the assistance of another network such as the Internet. It is highly used for file sharing of audio and video files.