The energy hitting an area over some time period. Is usually defined as the energy hitting an area over some time period.
In physics, intensity is the power transferred per unit area, where the area is an imagined surface that is perpendicular to the direction of propagation of the energy. In the SI system, it has units watts per square metre (W/m 2). It is used most frequently with waves (e.g. sound or light), in which case the average power transfer over one period of the wave is used. Intensity can be applied to other circumstances where energy is transferred. Intensity can be found by taking the energy density (energy per unit volume) at a point in space and multiplying it by the velocity at which the energy is moving. The resulting vector has the units of power divided by area. What does it mean? Waves carry energy, and the amplitude of a wave is generally a measure of how much energy the wave carries. In the same way, the displacement of a bow string, determines the amount of energy that propels the arrow. Energy is a positive quantity, so the amplitude is a positive number. However... Scientists don't usually talk about the amplitude of a light wave, since light isn't traveling in some substance like water or air. Luminous intensity. In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela, an SI base unit. Photometry deals with the measurement of visible light as perceived by human eyes. The human eye can only see light in the visible spectrum and has different sensitivities to light of different wavelengths within the spectrum. So the energy of light depends on both intensity and wavelength. To sum up, you now know a lot about waves and light: 1  How to measure wavelength. 2  That light wavelengths are often measured in units of angstroms. 3  That different wavelengths of light have different energies. Energy is a positive quantity, so the amplitude is a positive number. However... Scientists don't usually talk about the amplitude of a light wave, since light isn't traveling in some substance like water or air. In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit. Luminous intensity is the perceived power per unit solid angle. If a lamp has a 1 lumen bulb and the optics of the lamp are set up to focus the light evenly into a 1 steradian beam, then the beam would have a luminous intensity of 1 candela. So by level of light you probably mean light intensity which is something that can be measured. Light intensity is usually defined as the energy hitting an area over some time period. So in the case of a plant, a higher light intensity means more packets of light called “photons” are hitting the leaves. Answer 5: Click Here to return to the search form. I am not sure what you mean by level of light, but I will answer your question in to ways-in terms of the intensity of light and wavelength of light. Photosynthesis needs water, carbon dioxide, chlorophyll, light, and the right temperature. Light is an extremely important factor for the proces A narrower beam angle means a higher maximum luminous intensity for the same light output. LED packages are available in a range of beam angles from very narrow (near 6°) to quite wide (more than 100°); most illumination-grade LEDs are rated in terms of light output in lumens.  up vote 5 down vote. The light intensity $I$ is the power $P$, that irradiates an area $A$, $I=P/A$, therefore the units $\mathrm{W}\mathrm{m}^{-2}$. This means, that if you have two beams with equal intensities, the area is the same and the power has to be the same as well. You are probably confused by the relation between frequency and energy of a photon, $E_\nu = h\nu$. But this says just, what the energy of a single photon is. As @daaxix says, you have used intensity to mean irradiance. Irradiance is the amount of power the wave has delivered per unit area and hence, $W/m^2$. Both are quite similar in their definitions. Or in other words, the amplitude of the wave determines the
https://en.wikipedia.org/wiki/Intensity_(physics) http://cse.ssl.berkeley.edu/SegwayEd/lessons/light/measure3.html http://www.definitions.net/definition/luminous%20intensity http://cse.ssl.berkeley.edu/SegwayEd/lessons/light/measure3.html https://en.wikipedia.org/wiki/Luminous_intensity http://scienceline.ucsb.edu/getkey.php?key=4647 http://www.lrc.rpi.edu/programs/NLPIP/lightingAnswers/LED/luminousIntensityLightOutput.asp http://physics.stackexchange.com/questions/50006/intensity-of-light
what does intensity of light mean