# What is Light intensity: Definition and 87 Discussions

A light field camera, also known as plenoptic camera, captures information about the light field emanating from a scene; that is, the intensity of light in a scene, and also the direction that the light rays are traveling in space. This contrasts with a conventional camera, which records only light intensity.
One type of light field camera uses an array of micro-lenses placed in front of an otherwise conventional image sensor to sense intensity, color, and directional information. Multi-camera arrays are another type of light field camera. Holograms are a type of film-based light field image.

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1. ### I Light intensity required to shine a light through an opaque object

Pretty much, I was picturing a 1x1x1 meters cube of a dark colored, mostly uniform material (limited porosity, no crevices) with a small chamber in its interior - exactly where the center of mass should be. In it, a body emitting light is activated with the goal to find the intensity necessary...
2. ### Work and energy of electromagnetic wave with intensity I

a) ##\rho = \frac{I}{c} = \frac{F}{A}## for a perfect absorber ##F = ma## where ##a = \frac{c}{t}## ##\frac{I}{c} = \frac{mc}{tA}## ##I = \frac{I^2 tA}{mc^2} = \frac{P}{A}## ##P = \frac{I^2 tA^2}{mc^2} = \frac{W}{t}## ##W = \frac{I^2 t^2A^2}{mc^2}## I am unsure what A is. I think it should be...
3. ### Polarization and Light Intensity

Looked upon this and can't seem to find anything. The formula I=Icos^2theta seems to only work for polarization filters, which is not this case. On the other hand, the brewster's angle only c.aclates the angle when the REFLECTED light is polarized, not the REFRACTED light. Hence I am confused...
4. ### Young's experiment - lowering the light intensity of one slit

I think that what happens is that the amplitude becomes sqrt(2)/2A in the slit filtered, as opposed to A in the other slit. I suppose we will still get constructive interference from the slits, so the value (1+sqrt(2)/2)A will be reached as opposed to 2A in the usual experiment. However, the...
5. ### Light intensity profile along all radial distances

Hello, I have an ordinary light (not laser) collimated to produce a parallel beam. After traveling a distance in air, the beam has diverged significantly. The intensity decreases as the radial distance increases. Now I need to estimate the intensity profile along all radial distances inside the...
6. ### Light intensity at a distance -- UV light to kill bacteria

I have obtained seeds of a rare rhododendron species. These seeds are contaminated (experimentally determined). While I have tried several common methods, none decontaminated the seeds. Lately, I have read that so many joules of UV light at approximately 254nm will prevent replication and...
7. ### Calculation of Light Intensity

Hi all, I would like to calculate light intensity of a bulb from 0.5 meter. Which formula shoul i use? I have a PV. Dimensions are 12x12 cm. Bulb is 100 Watt. Thanks
8. ### I Plotting a far-field Intensity distribution

Hey, I'm attempting to plot a far-field intensity distribution using theoretical values, however I'm having difficulty with calculating the intensity using the following equation: $$I = I_o \frac {sin^{2}{b}}{b^{2}} \frac {sin^{2}{Ny}}{sin^{2}{y}}$$ where: $$y = \frac {kdX}{2f}$$ b =...
9. Z

### Photoelectric Effect, Light Intensity and Stopping Voltage

In a physics investigation we were required to use a Photo-Electric Effect Instrument (Shown in the attached pdf file), which was able to measure the current produced via the photoelectric effect. One of the objectives of the investigation was to alter the aperture size, and hence intensity of...
10. ### Far IR light intensity as a function of altitude

Homework Statement Hello, so I'm in a class that is building sensors and sending them up in a weather balloon. For my project, I am wanting to quantify the greenhouse effect by measuring the intensity of infrared light emitted as thermal radiation from the Earth as a function of height-- the...
11. ### Explaining Light intensity with EM Field Oscillations?

I have understood that the frequency of an EM wave is caused by the frequency by which a charged particle oscillates, which causes its electrical field to periodically change its strength with respect to a fixed location point at a distance from that particle. The more energy (heat) you add to...
12. ### Light intensity independant of frequency and E = hf

Isn't it weird that light intensity (which is time average of Poynting vector) doesn't depend of the light frequency, while the energy of a photon does ? From E = hf it seeems that frequency would have an impact of light energy flux (even time averaged). But intensity, which is a (time...
13. ### Calculating Scattered Light Intensity at Different Wavelengths

Homework Statement Light is scattered in cuvette by Reyleigh scattering, and is measured by monochromator. Light intesity is given by I(ν)=I0ν1/2 relationship What is scattered light intensity at λ = 400nm if at λ = 800nm is I800? Homework Equations Scattered light intensity is proportional...
14. ### Maximum light intensity underwater during seasons?

Hi, I was thinking if maximum light intensity underwater during seasons changes somehow. I firstly thought about considering monthly solar irradiance (http://neo.sci.gsfc.nasa.gov/view.php?datasetId=CERES_INSOL_M) however I thought this would have been biased at certain latitudes due to...
15. ### How can I correlate the light intensity and energy?

I need to know how much energy will I have for a certain intensity of ligh, I need this because I want to predict how much water will my solar oven evaporate for this light intesity (I can mesure the light intensity). I'd be very thankful if anyone helped me on this because I've searched a lot I...
16. ### Is there any relationship between light intensity and angle

Homework Statement I'm working on a project right now, which uses laser beams and part of the project requires me to find a mathematical model which relates angle of projection to the intensity of the light. Does anyone know of an equation(s) which relates the intensity and angle together...
17. ### Determining the light intensity in a double convex lens

Attached is an illustration of an image being demagnified using a double convex lens. I want to determine the intensity of the light (mW/cm2) if I were to put a lux meter at various locations after the convex lens given that the object is at a fixed location. The object is a monochromatic light...
18. ### How to calculate light intensity?

I am calculating the light intensity of Mercury. I was given the average distance from the Sun in AU's which is 0.39. Using the formula (1/(d^2)), I solved for the light intensity relative to Earth which I found to be 6.57. I need to find the light intensity in (w/(m^2))
19. ### Interference of light Intensity

An Interference pattern is produced by light of wavelength 490nm from a distant source incident on two identical parallel slits separated by a distance (between centers) of d=0.630mm. a) If the slits were very narrow what would be the angular position theta1 and theta2 of the first and second...
20. ### Mechanically, what does light intensity mean?

I am not sure what intensity actually looks like and means for light. Does this mean that ex red photon, that there are more than one photon that are superimposed on each other hitting the same spot?
21. ### Why shadows become dark when light intensity increases?

I observed following phenomena today: in my room with some lightings, there is a stuff toy placed in front of a wall. The ambient lighting doesn't cause any shadow on the wall currently. Now, I switched ON a torch and pointed it to a stuff toy which was kept in front of a wall and a shadow...
22. ### Is Pluto's Visible Light Intensity Equal to Earth's?

Is the visible light on the surface of Pluto equivalent in intensity to what it is on Earth? That is, is 1 lux = 1 lux even though it takes light that much longer to get there from the sun? Or are images of distant objects in the solar system taken with longer exposures?
23. ### What affects the intensity of different coloured lights?

Okay, so I have completed a practical where I used a light box and then placed different coloured plastics in front of the light and measured the light intensity of each colour. From the results I found that yellow, orange and violet had the highest intensities, with red and green having the...
24. ### How Do You Calculate Light Intensity in an Insulating Magnetic Material?

Homework Statement An electromagnetic wave with frequency 65.0Hz travels in an insulating magnetic material that has dielectric constant 3.64 and relative permeability 5.18 at this frequency. The electric field has amplitude 7.20×10−3V/m. What is the intensity of the wave? Homework Equations...
25. ### Light Intensity: Is it Decreasing at 1/r2?

Hello, If we consider a source of light (in a point x), is it wright to say that the intensity decreases in 1/r2 ? Thank you !
26. ### Light intensity and index of refraction

Hi. Will the amplitude of Poynting's vector change if the electromagnetic wave goes from one medium to another? Shouldn't the amplitude remain constant due to conservation of energy? I.e. the photon-density and velocity will change, but their total intensity remains the same. I could always do...
27. ### Light Intensity Model: Showing Minimal Difference at Off Point

Can someone assist with a simple model for the following question? I have looked on the net but cannot find anything on it. Say you are sat at a desk with the light bulb directly above you switched off and the rest on; so: on - on - on on - off - on on - on - on Each at distance r apart with...
28. ### Light intensity and wave behavior of light

Hello PF'ers, Why is it that two light-bulbs produce twice as much brightness as a single light-bulb would? If we restrict our attention to a single point in space where light from the two sources meet, the waves would cancel half of the time and reinforce half of the time, producing on...
29. ### Light intensity through a slit

Homework Statement After a laser beam passes through two thin parallel slits, the first completely dark fringes occur at ±14.0∘ with the original direction of the beam, as viewed on a screen far from the slits. A)What is the ratio of the distance between the slits to the wavelength of the...
30. ### Linear Polarizers and Light Intensity

Homework Statement Initially unpolarized light is shining on a series of six polarizers in a row. Each polarizer is rotated by the same angle, θ, relative to the previous polarizer. Choose a fraction (anything less than 1) as your final intensity. What is the angle, θ, such that the...
31. ### Why does the sun's heat & light intensity decrease over AU distances?

I'm a bit confused because the sun's radiation & heat are passing through space (with some passing through planets' atmospheres), and there is almost nothing in space, therefore, how does that immense heat & light just diminish over AU distances when its going through almost nothingness? What...
32. ### General equation for light intensity entering half circle

Hello, I am currently working on a problem to calculate the light that makes it through a half circle. For example, say I put a cylinder out in the sun, where the intensity is known to be 1030 W/m^2. I would like to compute the intensity/energy/power that makes it into this. Now, given the...
33. ### What affects the light intensity and light output geometry?

These are some of the factors I brainstormed that goes into the functionality of a spotlight: 1) Light output of the light source (measured in luminous flux, if I recall correctly) 2) The reflective potential of the reflectors surrounding the light source 3) The geometry of the reflectors...
34. ### LED - Measuring light intensity

what type of circuit would you draw for this? and how would you actually measure the light intensity of an LED. say you had multiple LEDs and you wanted to compare the light intensity of all of them. how would you do this with with circuit?
35. ### Furnace flame- light intensity

Hi Guys, A basic oxygen furnace is very large 400 ton vessel that steel is refined in. during the refining process oxygen is blown into the steel. during this process there is a flame at the mouth of the furnace, this is what I am interesting in. during the process the flame changes in size...
36. ### Calculate light intensity after reflection/refraction

Hi all, I'm playing around with an autocue type of display. So basically, there is an LCD display that reflects light on a piece of plexi, at a 45 degrees angle. I know that the LCD dispay is horizontally polarized, so I can calculate the refraction and reflection coefficients of the...
37. ### Calculating Light Intensity from Sunlight for Solar Food Dehydrator

Hi there, im doing school project regarding Solar Food Dehydrator. Can tell me what is the formula to calculate the light intensity from the sunlight?
38. ### Light intensity of UV component from a xenon lamp

I have a 100watt xenon lamp , the UV component comprises of 5-6% of the total spectrum emitted by the xenon lamp . How do I calculate at what power is the UV light emitted ? Is the whole spectrum being emitted at 100 W or is the power distributed through the spectrum? How is this...
39. ### Light Intensity transmitted through the polarized and analyzer

Homework Statement Here is the question:Unpolarized light of intesity Io is incident on a polarizer-analyzer pair. If the angle between the polarizer and analyzer is 21°, what light intensity is transmitted through the polarizer and analyzer respectively? Your answers will be in terms of...
40. ### Relationship between light intensity and current

I'm doing a solar cell characterization project. But due to some fault in my solar simulator(I'm getting different results from another set up), I'm now figuring a way to check the intensity of light shone by my simulator on cell. I'm trying to obtain it from the corrected data of my cell (Isc...
41. ### Light intensity and polarization

I have read about light and polarization. One thing I don't understand though... If you would look through a circular polarization filter, you notice that the light is less intense. But if you look at photons that are unpolarized; they become polarized when they go through the filter. I have...
42. ### Does greater light intensity imply greater energy?

Since light intensity increases with the number of photons, and the photon can be viewed as energy, would energy be proportional to intensity of light? Also since energy is inversely proportional to the wavelength of light, this would mean that the intensity of light is also inversely...
43. ### Help understanding light intensity

I have a problem understanding the intensity of light. Let's assume a monochromatic light of a single wavelength. The energy of the wave is constant and equal to h* f where h is the Planck's constant and f the frequency of the wave. The intensity of this wave is its energy divided by a given...
44. ### Determining LED light intensity from its radiant power

I have LEDs of 0.7mW, but for my experiments, I want my values to be in light intensity unit - W/cm2. I cannot figure out how to do the conversion.
45. ### How Do You Calculate UV Light Intensity Needed to Kill Germs on an AC Coil?

Hello, I need to calculate intensity of light at a distance of 24 inch from a tubular light source with a light intensity rating specified at 3.6 microwatts/sq.cm. per inch of lamp. The light is a UV light which is to illuminating a cooling coil in air conditioning system. Supposedly there...
46. ### Second Harmonic Generation: Light Intensity & Efficiency

OK so i know it is possible to double the frequency of a light beam by using second harmonic generation by passing the beam through a non-linear crystal; however i am unclear as to the required intensity of light beam that is needed to achieve efficient conversation. Would it be possible to...
47. ### Has anyone measured the light intensity given off in a fusion reactor?

I was just wondering if, through all the fusion test done over the years, if anybody has ever mesaured the lux given off dureing a reaction?
48. ### Effect of altering incident light intensity on absorption

Hi all, Physics was never my strong point at school, yet here I am looking at the differences between three types of graduated light filter for a Health Sciences Masters degree. I'm in the process of writing up, and one of my sets of results is a bit bewildering. Basically, I measured the...
49. ### Voltmeter to Measure Light Intensity

measure of light intensity using a voltmeter? relationship between voltage and light intensity
50. ### Single Slit Diffraction light intensity

Homework Statement This is the light intensity on a viewing screen behind a rectangular opening in a screen. Is the shape of the opening (1), (2), or (3)? Homework Equations w=(2λL)/a where w is the width of the central maximum, L is the distance to the viewing screen, and a is...