This is by far the least precise way of getting a light reading, but it should give you a ballpark estimate of your lighting conditions. If you’re looking for a precise measurement and willing to take a couple of minutes to figure it out, read on.

The sensor will need to be angled towards the light, NOT TOWARDS YOUR PLANT. We don’t care how much light is bouncing off the leaves, we want to measure the light from the source. The method we use is to hold the light meter as close to the leaves of the plant as possible, with the sensor pointed away from the plant, in the direction of the incoming light. If your plant is against a wall, you can point the sensor against the wall to get an idea of how much light the back side of your plant is getting. This is why plants will often defoliate on the side that’s not facing the window, and why it’s so important to rotate your plants.

Set your range. Push the RANGE button until you start getting a reading. If your reading is an unmoving "1 .    " don’t panic. The RANGE button is simply moving the decimal point forward. You will probably need to press the button a few times to find the right range for your space. The brighter it is, the more times you’ll need to push this button.

We’ll delve into specifics below, but first it’s important we talk about a unit of measurement often used in conjunction with plants. Growing plants depends on giving them the right quality of light, which means providing them with a spectrum of light matching that of our galaxy’s sun, or at least a close(ish) approximation. However what’s much, much more important is providing them with a good quantity of light.

A Polaroid filter is able to polarize light because of the chemical composition of the filter material. The filter can be thought of as having long-chain molecules that are aligned within the filter in the same direction. During the fabrication of the filter, the long-chain molecules are stretched across the filter so that each molecule is (as much as possible) aligned in say the vertical direction. As unpolarized light strikes the filter, the portion of the waves vibrating in the vertical direction are absorbed by the filter. The general rule is that the electromagnetic vibrations that are in a direction parallel to the alignment of the molecules are absorbed.

Light measureapp

5. Take note of the measurements. Write them down if you’re looking for a good spot. You can compare and contrast the best lit locations for your plant. Skip ahead to the How to Interpret Foot Candles section for information on how to utilize your reading.

It is possible to transform unpolarized light into polarized light. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as polarization. There are a variety of methods of polarizing light. The four methods discussed on this page are:

Our model of the polarization of light provides some substantial support for the wavelike nature of light. It would be extremely difficult to explain polarization phenomenon using a particle view of light. Polarization would only occur with a transverse wave. For this reason, polarization is one more reason why scientists believe that light exhibits wavelike behavior.

Foot candles are an imprecise form of measurement, but they give us a good idea of how much light a plant is getting. Once we have a hard numerical measurement of the intensity of light in a space, we can start looking at what plants would do well.

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What is the SI unit oflight

3. Point your camera. You’re essentially using your phone’s camera to measure brightness. It’s important that you point the camera IN THE DIRECTION OF THE LIGHT. Light Meter gives you the option of using the front or the back camera, and either option will work.

There is no clear consensus on what levels of light individual plants need, and Foot Candle recommendations are all over the map. However, through our sister company Greenery NYC we have the advantage of monitoring plants over the course of years, and have come to rely on the following levels as the bare minimum in which a plant can survive. Many plants classified as “indoor” plants are actually tropical understory plants, which means they have adapted to the filtered light available on the jungle floor, so another note to consider is that too much direct sun can burn plants. However, like humans, plants are adaptable to different lighting conditions, and over time can adjust to a variety of environments. Think about a New Yorker taking a winter exodus to the beaches of Miami: without preventative measures like sunscreen, the sudden shift in environment can be damaging and in extreme cases deadly.

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Although the term is anachronistic, foot candles are still a common form of measurement in the horticulture community. Dictionary.com defines a foot candle as the following:

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Lightmeasurement for plants

The transverse nature of an electromagnetic wave is quite different from any other type of wave that has been discussed in The Physics Classroom Tutorial. Let's suppose that we use the customary slinky to model the behavior of an electromagnetic wave. As an electromagnetic wave traveled towards you, then you would observe the vibrations of the slinky occurring in more than one plane of vibration. This is quite different than what you might notice if you were to look along a slinky and observe a slinky wave traveling towards you. Indeed, the coils of the slinky would be vibrating back and forth as the slinky approached; yet these vibrations would occur in a single plane of space. That is, the coils of the slinky might vibrate up and down or left and right. Yet regardless of their direction of vibration, they would be moving along the same linear direction as you sighted along the slinky. If a slinky wave were an electromagnetic wave, then the vibrations of the slinky would occur in multiple planes. Unlike a usual slinky wave, the electric and magnetic vibrations of an electromagnetic wave occur in numerous planes. A light wave that is vibrating in more than one plane is referred to as unpolarized light. Light emitted by the sun, by a lamp in the classroom, or by a candle flame is unpolarized light. Such light waves are created by electric charges that vibrate in a variety of directions, thus creating an electromagnetic wave that vibrates in a variety of directions. This concept of unpolarized light is rather difficult to visualize. In general, it is helpful to picture unpolarized light as a wave that has an average of half its vibrations in a horizontal plane and half of its vibrations in a vertical plane.

Polarization has a wealth of other applications besides their use in glare-reducing sunglasses. In industry, Polaroid filters are used to perform stress analysis tests on transparent plastics. As light passes through a plastic, each color of visible light is polarized with its own orientation. If such a plastic is placed between two polarizing plates, a colorful pattern is revealed. As the top plate is turned, the color pattern changes as new colors become blocked and the formerly blocked colors are transmitted. A common Physics demonstration involves placing a plastic protractor between two Polaroid plates and placing them on top of an overhead projector. It is known that structural stress in plastic is signified at locations where there is a large concentration of colored bands. This location of stress is usually the location where structural failure will most likely occur. Perhaps you wish that a more careful stress analysis were performed on the plastic case of the CD that you recently purchased.

Diffusing a light and increasing its surface area are clearly NOT the same thing (even though one sometimes causes the other).

Write down the value of your reading and continue to the next section for information on how to use Foot Candles to assess your space.

Polarization is also used in the entertainment industry to produce and show 3-D movies. Three-dimensional movies are actually two movies being shown at the same time through two projectors. The two movies are filmed from two slightly different camera locations. Each individual movie is then projected from different sides of the audience onto a metal screen. The movies are projected through a polarizing filter. The polarizing filter used for the projector on the left may have its polarization axis aligned horizontally while the polarizing filter used for the projector on the right would have its polarization axis aligned vertically. Consequently, there are two slightly different movies being projected onto a screen. Each movie is cast by light that is polarized with an orientation perpendicular to the other movie. The audience then wears glasses that have two Polaroid filters. Each filter has a different polarization axis - one is horizontal and the other is vertical. The result of this arrangement of projectors and filters is that the left eye sees the movie that is projected from the right projector while the right eye sees the movie that is projected from the left projector. This gives the viewer a perception of depth.

The first filter will polarize the light, blocking one-half of its vibrations. The second filter will have no affect on the light. Being aligned parallel to the first filter, the second filter will let the same light waves through.

Unpolarized light can also undergo polarization by reflection off of nonmetallic surfaces. The extent to which polarization occurs is dependent upon the angle at which the light approaches the surface and upon the material that the surface is made of. Metallic surfaces reflect light with a variety of vibrational directions; such reflected light is unpolarized. However, nonmetallic surfaces such as asphalt roadways, snowfields and water reflect light such that there is a large concentration of vibrations in a plane parallel to the reflecting surface. A person viewing objects by means of light reflected off of nonmetallic surfaces will often perceive a glare if the extent of polarization is large. Fishermen are familiar with this glare since it prevents them from seeing fish that lie below the water. Light reflected off a lake is partially polarized in a direction parallel to the water's surface. Fishermen know that the use of glare-reducing sunglasses with the proper polarization axis allows for the blocking of this partially polarized light. By blocking the plane-polarized light, the glare is reduced and the fisherman can more easily see fish located under the water.

Lightmeasurement device

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To see our recommendations, go to our Online Store and click the Light Requirements section on the Filter Bar. Plants listed as low light on our site can survive on 25 FC. High light plants need at least 150 FC. Remember there’s going to be variation in your readings, depending on the time of day, weather conditions, indoor lighting etc. But as a general rule, you should never place a plant like a fiddle leaf fig tree in an area with 20 FC. There are plants sold as interior plants that require even higher levels of light, such as aralias and podocarpus, but although these are marketed as indoor plants we don't consider them viable for long-term success except in areas with extreme levels of light, such as areas with an abundance of floor to ceiling windows.

Polarization of light by use of a Polaroid filter is often demonstrated in a Physics class through a variety of demonstrations. Filters are used to look through and view objects. The filter does not distort the shape or dimensions of the object; it merely serves to produce a dimmer image of the object since one-half of the light is blocked as it passed through the filter. A pair of filters is often placed back to back in order to view objects looking through two filters. By slowly rotating the second filter, an orientation can be found in which all the light from an object is blocked and the object can no longer be seen when viewed through two filters. What happened? In this demonstration, the light was polarized upon passage through the first filter; perhaps only vertical vibrations were able to pass through. These vertical vibrations were then blocked by the second filter since its polarization filter is aligned in a horizontal direction. While you are unable to see the axes on the filter, you will know when the axes are aligned perpendicular to each other because with this orientation, all light is blocked. So by use of two filters, one can completely block all of the light that is incident upon the set; this will only occur if the polarization axes are rotated such that they are perpendicular to each other.

Lightmeasurement unit K

A light meter is a great, reliable way to measure light. We use the Dr. Meter light meter, which has proven to be a reliable tool for the price. We’ll be walking through the steps on how to use this specific device, but it’s a simple process that should translate to all light meters on the market.

NOTE: If you’re used to working with lux or are using an instrument that only measures lux, please note there’s a direct conversion between the two units of measurement.

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For hobbyists and interiorscapers like ourselves, we don’t need expensive tools like PAR meters or spectrometers. These devices that can be useful for commercially growing plants, but let’s be honest: most of you are just trying to keep your plants alive and happy enough to put out a new leaf every once in a while. For this purpose, talking about light in terms of foot candles will do the trick.

A light wave is an electromagnetic wave that travels through the vacuum of outer space. Light waves are produced by vibrating electric charges. The nature of such electromagnetic waves is beyond the scope of The Physics Classroom Tutorial. For our purposes, it is sufficient to merely say that an electromagnetic wave is a transverse wave that has both an electric and a magnetic component.

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2000331 — A variety of components make up a complete fiber optic lighting system, including the illuminator, light guide, port, connector, coupler, ferrule, and fixture.

Polarization can also occur by the refraction of light. Refraction occurs when a beam of light passes from one material into another material. At the surface of the two materials, the path of the beam changes its direction. The refracted beam acquires some degree of polarization. Most often, the polarization occurs in a plane perpendicular to the surface. The polarization of refracted light is often demonstrated in a Physics class using a unique crystal that serves as a double-refracting crystal. Iceland Spar, a rather rare form of the mineral calcite, refracts incident light into two different paths. The light is split into two beams upon entering the crystal. Subsequently, if an object is viewed by looking through an Iceland Spar crystal, two images will be seen. The two images are the result of the double refraction of light. Both refracted light beams are polarized - one in a direction parallel to the surface and the other in a direction perpendicular to the surface. Since these two refracted rays are polarized with a perpendicular orientation, a polarizing filter can be used to completely block one of the images. If the polarization axis of the filter is aligned perpendicular to the plane of polarized light, the light is completely blocked by the filter; meanwhile the second image is as bright as can be. And if the filter is then turned 90-degrees in either direction, the second image reappears and the first image disappears. Now that's pretty neat observation that could never be observed if light did not exhibit any wavelike behavior.

Referring to the above question, the glare is the result of a large concentration of light aligned parallel to the water surface. To block such plane-polarized light, a filter with a vertically aligned polarization axis must be used.

Lightintensity

In the same manner, two Polaroid filters oriented with their polarization axes perpendicular to each other will block all the light. Now that's a pretty cool observation that could never be explained by a particle view of light.

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The exposure meter built into your camera is a reflective light meter, meaning that it measures light reflected from a subject. The other type of exposure meter ...

Lightmeasurement unit lux

1. Suppose that light passes through two Polaroid filters whose polarization axes are parallel to each other. What would be the result?

The same way humans need to eat organic matter to function, plants need light to photosynthesize. It’s their food. Without adequate lighting for your plant, it will become anemic and eventually die. Second to overwatering, inadequate lighting is the number one killer of plants, so be sure that if you get a plant that loves bright, indirect light, you put it in a place that’s going to nourish it for the long term.

Polarization also occurs when light is scattered while traveling through a medium. When light strikes the atoms of a material, it will often set the electrons of those atoms into vibration. The vibrating electrons then produce their own electromagnetic wave that is radiated outward in all directions. This newly generated wave strikes neighboring atoms, forcing their electrons into vibrations at the same original frequency. These vibrating electrons produce another electromagnetic wave that is once more radiated outward in all directions. This absorption and reemission of light waves causes the light to be scattered about the medium. (This process of scattering contributes to the blueness of our skies, a topic to be discussed later.) This scattered light is partially polarized. Polarization by scattering is observed as light passes through our atmosphere. The scattered light often produces a glare in the skies. Photographers know that this partial polarization of scattered light leads to photographs characterized by a washed-out sky. The problem can easily be corrected by the use of a Polaroid filter. As the filter is rotated, the partially polarized light is blocked and the glare is reduced. The photographic secret of capturing a vivid blue sky as the backdrop of a beautiful foreground lies in the physics of polarization and Polaroid filters.

Pick a spot in your house where you’re considering placing your plant. At the brightest time of the day, usually around noon, hold your hand up and look at the shadow.

Lightmeasurement unit

One of the biggest difficulties we notice among our clients is their ability to assess the proper lighting for their plants. It’s not easy. The human eye automatically compensates for brightness, which makes our ability to judge light levels deceiving. Indoor lights often complicate the issue because what looks “bright” may not be anywhere close when measured with an instrument. At Greenery Unlimited we’ve assessed thousands of spaces, and the first part of our job is always matching the right environment with the right plant. Below we will detail three basic methods for assessing light in your home or office: a quick, somewhat accurate eye test, a somewhat more accurate app that can be installed on your smart device, and instructions for using a physical instrument called a Light Meter that can be purchased for about $35.

2. Light becomes partially polarized as it reflects off nonmetallic surfaces such as glass, water, or a road surface. The polarized light consists of waves vibrate in a plane that is ____________ (parallel, perpendicular) to the reflecting surface.

The alignment of these molecules gives the filter a polarization axis. This polarization axis extends across the length of the filter and only allows vibrations of the electromagnetic wave that are parallel to the axis to pass through. Any vibrations that are perpendicular to the polarization axis are blocked by the filter. Thus, a Polaroid filter with its long-chain molecules aligned horizontally will have a polarization axis aligned vertically. Such a filter will block all horizontal vibrations and allow the vertical vibrations to be transmitted (see diagram above). On the other hand, a Polaroid filter with its long-chain molecules aligned vertically will have a polarization axis aligned horizontally; this filter will block all vertical vibrations and allow the horizontal vibrations to be transmitted.

A picket-fence analogy is often used to explain how this dual-filter demonstration works. A picket fence can act as a polarizer by transforming an unpolarized wave in a rope into a wave that vibrates in a single plane. The spaces between the pickets of the fence will allow vibrations that are parallel to the spacings to pass through while blocking any vibrations that are perpendicular to the spacings. Obviously, a vertical vibration would not have the room to make it through a horizontal spacing. If two picket fences are oriented such that the pickets are both aligned vertically, then vertical vibrations will pass through both fences. On the other hand, if the pickets of the second fence are aligned horizontally, then the vertical vibrations that pass through the first fence will be blocked by the second fence. This is depicted in the diagram below.

If you have an iPhone, Light Meter has a function for measuring foot candles. It costs $1.99 and is a good purchase if you’re unsure about the placement of a new plant. This guide will cover using this app, but really there are tons of light meter apps out there, and although most of them don’t measure in foot candles, they do measure in LUX, which is easy to translate to foot candles using the conversion rate listed above.

3. Consider the three pairs of sunglasses below. Identify the pair of glasses is capable of eliminating the glare resulting from sunlight reflecting off the calm waters of a lake? _________ Explain. (The polarization axes are shown by the straight lines.)

The most common method of polarization involves the use of a Polaroid filter. Polaroid filters are made of a special material that is capable of blocking one of the two planes of vibration of an electromagnetic wave. (Remember, the notion of two planes or directions of vibration is merely a simplification that helps us to visualize the wavelike nature of the electromagnetic wave.) In this sense, a Polaroid serves as a device that filters out one-half of the vibrations upon transmission of the light through the filter. When unpolarized light is transmitted through a Polaroid filter, it emerges with one-half the intensity and with vibrations in a single plane; it emerges as polarized light.