# Light intensity and power relationship

### Intensity – The Physics Hypertextbook

By definition, the intensity (I) of any wave is the time-averaged power (⟨P⟩) it .. We get this thing again — the intensity-pressure amplitude relationship. While we have not emphasized it so far, electric and magnetic fields both contain energy. The total amount of energy depends on the values of. Also, how can I calculate the total power, or total intensity, of this light beam from the solar By the simple relationship between wavelength and frequency ν.

Density fluctuations are minuscule and short lived. The period of a sound wave is typically measured in milliseconds. There are some optical techniques that make it possible to image the intense compressions are rarefactions associated with shock waves in air, but these are not the kinds of sounds we deal with in our everyday lives. Pressure fluctuations caused by sound waves are much easier to measure.

Animals including humans have been doing it for several hundred million years with devices called ears. Humans have also been doing it electromechanically for about a hundred years with devices called microphones.

All types of amplitudes are equally valid for describing sound waves mathematically, but pressure amplitudes are the one we humans have the closest connection to. In any case, the results of such measurements are rarely ever reported.

Instead, amplitude measurements are almost always used as the raw data in some computation. When done by an electronic circuit like the circuits in a telephone that connect to a microphone the resulting value is called intensity. When done by a neuronal circuit like the circuits in your brain that connect to your ears the resulting sensation is called loudness. The intensity of a sound wave is a combination of its rate and density of energy transfer.

It is an objective quantity associated with a wave. Loudness is a perceptual response to the physical property of intensity.

### Intensity (physics) - Wikipedia

It is a subjective quality associated with a wave and is a bit more complex. In a multimode laser beam, generated in a laser where higher-order transverse resonator modes are excited, the shape of the transverse intensity profile can undergo significant changes as the relative optical phases of the modes change with time. The peak intensity can then vary, and may occur at locations at some distance from the beam axis. The term intensity is often used in a non-quantitative or not very precise way, and not clearly distinguished from the optical power.

Physics - Electromagnetic Radiation (2 of 5) Ex: Intensity of Light

For example, the intensity noise normally refers to noise fluctuations of the optical power, rather than the intensity. Optical intensities are relevant in various situations: In conjunction with transition cross sectionsintensities govern the rates of optical transitions, e. Strong saturation of an optical transition in the steady state occurs when the intensity exceeds the saturation intensity.

## 3. Energy and Intensity of Light

The refractive index change via the Kerr effect in a transparent medium is the nonlinear index times the local intensity. Laser-induced damage of a medium may occur for intensities above a certain damage threshold, which however can usually only be reached with optical pulsesand then depends on the pulse duration. Extremely high peak intensities can be achieved with amplified ultrashort pulses.

For intensities of e. The radiation pressure of light incident on a surface is proportional to the optical intensity.

Beam profilers can be used for measuring the shape of the intensity profile of a laser beam.