Light intensity Definition and 82 Threads

Homework Statement using the same film and level of illumination two pictures are taken, one with double the f number of the other. for both films to receive the same total light energy, what factor must the required time of exposure change for the picture with double the f number...

Hello I am trying to understand Malus' Law and the Intensity of light. Let's say I have three polarizers. The first polarizer and the last polarizer have the same axis of polarization. The middle polarizer can be rotated to an angle \theta I know that Malus's Law for the intensity of light is I...

Homework Statement You put a point source of light (S) a distance (d) in front of screen (A). How is the light intensity at the center of the screen changed if you put a completely reflecting mirror (M) a distance (d) behind the source? M-----d-----S-----d-----A Homework Equations...

I've got an experiment coming up where I have to find out how the resistance in a circuit changes as more layers of 'tracing paper' are added onto a LDR i.e. as more paper is added the light intensity will fall and as a result the resistance through the circuit will increase. I am testing for...

Hi, If light intensity is determined by the number of photons, what determines the number of photons? A higher energy wave does not mean more photons, right? A higher energy wave just means that the photons have more energy, because higher frequency means more energy? How come a...

Unpolarized light from an incandescent lamp has an intensity 176 Cd as measured by a light meter. What is the intensity reading on the meter when two ideal are inserted between the bulb and the meter with their axis of polarization making an angle of θ = 40.0° relative to each other? Express...

How would I go about converting 59.7 mw/m^2 to lux? I would appreciate any help I can't find an equality.

I used a Planck's constant kit and varied the frequency of light in order to verify Planck's constant. However I have also used apertures to vary the surface area and I am quite confused as to what to do with this data to relate it back to Planck's constant. The data is as seen in in the...

Homework Statement A flashlight lights up a wall a distance L from the small bulb whose wattage is given by W. The conical beam emerges from the flashlight at an angle theta. What is the intensity of light as it hits the wall a distance L from the bulb? Homework Equations I = Power/Area...

Homework Statement A 60-cd lamp and a lamp of unknown intensity are placed 3m apart. A light meter is moved between the two lamps until it reads the same illuminance from both lamps. The light meter is then 1.5 m away from the 60-cd lamp. What is the intensity of the other lamp? Homework...

Hi, I'm a junior and I have been assigned a lab that I has completely me blown away! We are to find the intensity of our given light source on a solar panel at different distances. My partner and I understand how to complete the lab, but there is another part of the grade. We are assigned to...

Homework Statement Unpolarized light has intensity 15W/m^2 and is incident on a sheet of polarizing material whose transmission axis makes an angle of 25 degrees with the vertical. A second polarizer, whose transmission axis is horizontal, is located just past the first. (a) What is the...

Homework Statement Unpolarized light of intensity I0 passes through two pieces of Polaroid sheet. The second piece is rotated so that the intensity of the transmitted light goes to zero. A third piece of Polaroid is inserted between the two pieces. Calculate the intensity as a function of...

stuck on light intensity problem... 1. Homework Statement http://s685.photobucket.com/albums/vv212/dewdr0p714/?action=view&current=physicsexam2q5withoutphotocell.jpg A conducting rod slides down 2 frictionless copper tracks at a constant velocity. There is a .50 T magnetic field...

What is the relationship between light intensity and irradiance? How do I convert one to the other?

I'm doing a report for biology about the relation betweem light intensity and photosynthetic rate. My results showed that as light intensity decreases, so does oxygen production. I said in my discussion that light rays that must travel longer distances will lose energy and appear dimmer than...

Homework Statement For a science project, you would like to horizontally suspend an 8.5 by 11 inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is 1.0 g, what light intensity will you need? Homework Equations...

Hello everybody, I am trying to measure the light intensity of light going through a plexiglass (U Shaped) in a fish tank using led. I would love to see accurate voltage measurements due to the change in the liquid level. I tried photodetecr transistors; it wasn't accurate at all. I am thinking...

Hi everyone, In a light bulb, as we increase the temperature of the light bulb, the colour produced by the light bulb changes from red to blue ( intensity vs frequency curve shifts to the left). But if i want to have a red bulb with higher intensity ( i.e. brighter red) without...

I've been searching through the internet and some of my optics books, but nowhere was I able to find the derivation of the law for a camera lens, that the intensity of light that comes on the film or chip is proportional to \frac{D^2}{f^2}=N^2, where D is the aperture diameter, f the focal...

[SOLVED] Light Intensity question The light (electromagnetic) output of a bulb is 40 W. How much energy passes through a 40 cm^2 area element aligned perp. to the light rays? I know that I = Power/Area, but I thought that Power = W(aka. energy) /t , and the problem has no reference to time...

Hi Guys, I am new to this forum and have a "quick" question. Say you had a laser pointer and you directed the laser through a glass block and then to a LDR why would the light intensity recorded be lower than without the glass block? What is happening to the light when it is in the glass...

This is the question Find the intensity of a light source that produces an illumination of 7.50 lux at a distance of 30m from the source. This what I get but it's wrong 84823 This is the formula E = Illumination I = luminous intensity of the source ( in lumens) r= distance...

Please check to see if my solution is correct: Question: If a light source were increased by a factor of 2 in intensity, what would happen to the value of KE_max of each photoelectron? My solution: KE_max would stay the same because increasing the intesity by a factor of two would only...

Homework Statement For my physics coursework, I have to design a laboratory experiment using an LDR to investigate how intensity of light emitted from a lamp varies with wavelength. In the procedure I will use diffraction gratings to separate light into wavelengths. The problem I am having is...

Homework Statement For my physics coursework, I have to design a laboratory experiment using an LDR to investigate how intensity of light emitted from a lamp varies with wavelength. In the procedure I will use diffraction gratings to separate light into wavelengths. The problem I am having is...

From using a magnifying lens under the Sun, I gather it can focus all or most of the light impinging on its surface area to a small spot and that is how it is able to create a greater intensity light at its focus (disregarding absorption in the lens.) Correct? What portion of the total light...

Hi, I just came to this problem when I was studying the photoelectric effect, what is the exact definition for "light intensity" ? Is it just n (the number of photons) or is it E/(A.t) where E=nhf ? The latter can be the same as the former in comparison when we suppose the frequency is the...

Hey dudes and dudettes, loving the forum here. Will be around quite a bit for the next year or so hopefully.. Just a quick question, any help would be appreciated so much.. I'm doing my A2 main coursework, that's the one you do when you're 18 for all the American types, and was wondering...

This is the schematic of my project (figure7)...but I don't know how to add display (ICL7107) using eagle, and how to power display .. how to connect the output voltage of stage2(second opamp) to the display? http://www.seas.upenn.edu/~ee205/Labs97S/Lab7/Lab7.html anyway , take a look at...

affect the infiltration of water in the soil? :bugeye: Thank you thank you thank you.. :]

I have a few pretty simple questions that I can't seem to find a clear answer to on the net... The energy of a light wave is directly proportionate to frequency and inversely proportionate to wavelength. This is due to the energy of a Photon being equal to hf. "f" is a constant, so the...