About Intensity of Light
Light is required for human eyesight. Light reflects off surfaces and enters the eyes, where it passes through the cornea and pupil to produce a picture on the retina. The eye is sensitive to a wide range of light intensities but loses its capacity to distinguish detail at low levels. As a result, precise work such as surgery, measuring, or assembly is best done under strong light. Working in dim illumination leads to weariness and blunders. When the light levels are low, industrial accidents become more prevalent. Furthermore, how effectively people can see a presentation and capture decent images is determined by the intensity of illumination of the light. In order to better grasp light intensity measurement, we'll look at what intensity of light is and how measurement of light occurs.
What Exactly is Light?
Light is a kind of electromagnetic energy that moves like a wave through space. Those waves, like microwaves and x-rays, have a wavelength and a frequency. Humans, on the other hand, have receptors that can detect energy with wavelengths between 400 and 700 nm and convert it into visuals. Colors are assigned to individual wavelengths. Light having a wavelength of roughly 420 nm is considered blue, 525 nm is considered green, and 635 nm is considered red. Longer wavelengths are referred to as infrared (which is perceived as heat), whereas shorter wavelengths are referred to as ultraviolet and finally x-rays.
Heat-based light sources (also known as "incandescent" light sources) emit electromagnetic energy at all wavelengths, which is why they seem white. The temperature of the source influences the distribution of wavelengths within that light. Fluorescent lights seem white due to fluorescence from a coating on the glass or tube, but LEDs emit light at only one wavelength.
What is the Intensity of Light?
The word intensity refers to the pace at which light spreads over a particular area's surface at a distance from the source. The intensity changes depending on the distance from the source and the source's power. The power of a light source describes the rate at which light energy is released by the source. The intensity of light varies according to the lighting source, and there are high and low light intensity fixtures, lamps, and bulbs. Great-intensity discharge lamps, for example, provide a high amount of light, whereas fluorescent lights produce a "cool" or low-intensity light.
When it comes to gardening, different light intensities have unique applications. Young plants, for example, require lower light intensity than vegetative and flowering plants. Furthermore, indoor cultivation needs a greater light intensity in general, because, unlike a greenhouse, there is no natural light source coming in, and the intensity of the lamp(s) must compensate for this.
Unit of Light Intensity
The candela is the fundamental light intensity unit, ostensibly the light emitted by one candle, or more accurately, "a source emitting monochromatic radiation with a frequency of 540 × 1014hertz and a radiant intensity in that direction of 1/683 watt per steradian." A light source, such as an incandescent bulb's filament, emits light in all directions. It is effectively at the centre of a sphere of emitted light (which is why light units reference the steradian). The "luminous flux" is the total energy of all the light emitted.
A lumen is a unit of light intensity equal to one candela per steradian, which is the most common unit of light intensity. The amount of lumens falling on a surface, which is denoted as lux, is what counts most when it comes to gauging light intensity. As a result, one lux equals one lumen per square metre, with brightness proportional to distance from the source. (In the United States, light intensity is commonly expressed in foot-candles.) One lumen per square foot is equal to one foot-candle).
How to Measure Light Intensity ?
When photons collide with a sensor, their energy is transformed to an electrical charge. The greater the amount of light that touches the surface, the more charge is generated up. In general, the two are intertwined. In the measuring electronics, a calibration transforms current or voltage to a lux value. To make matters more complicated, the human eye is not equally sensitive to all wavelengths of light and is more sensitive to green.
Thus, if equal intensities of blue light and green light fall on a metre, the human viewer will see more green light even though the raw lux value is the same. To address this, lux metres are set to assume light with the spectral distribution of tungsten-filament lighting in the home. This is known as CIE (i.e, International Commission on Illumination) standard illuminant A, and it modifies the raw intensity measurement to better coincide with human sense of brightness. All incandescent lighting applications should employ CIE standard illuminant A.
Light Intensity Measurement Equipment
Rugged Portable Environmental Meters for RPM and light intensity meter are easy-to-use handheld equipment for measuring the intensity of light. Based on the CIE Standard Illuminant A, these units are suited for usage in places with incandescent lighting and will offer a reading with a minimal error under fluorescent illumination with a measuring range of 1 to 200,000 lux (0 to 18,580 foot candles).
This device is suitable for anybody who needs to check light levels in indoor work locations, such as photographers, theatre set designers, interior designers, and filmmakers. It can be used outside where comparable values or ratios are adequate, but due to its CIE calibration, it should not be depended on for exact intensity measurements.
Definition of Luminous Intensity and Its Example
The amount of visible light emitted in unit time per unit solid angle is referred to as luminous intensity. The lumen is the unit representing the amount of light that flows from a source in one second (the luminous power, or luminous flux). The luminosity is assessed using visual sense as a criterion. The human eye is most sensitive to light at a wavelength of 555 nanometres (10-9metre); at this wavelength, there are 685 lumens per watt of radiant power, or radiant flux (the luminous efficiency), although the luminous efficiency is lower at other wavelengths. An ordinary candle, which generates light with a luminous intensity of around 1 cd, is an example of luminous intensity.
FAQs on Light Intensity
1. What are the situations in which light measurement is necessary?
Ans: The primary reasons for measuring light intensity are to guarantee that minimum lighting criteria are met and to establish suitable exposure periods in photography and filmmaking. The four most prevalent cases are shown below.
Ergonomics and Safety: Light intensity is only assessed reactively in some companies, usually after a fall or other disaster. A more practical strategy would be to do a lighting study, noting the levels of light across the workplace. If areas are determined to be below the minimum acceptable standards, an improvement plan can be put in place.
Photography and Cinematography: The intensity of light is crucial to photography. When there isn't enough light, a photographer must either lengthen the exposure time or open up the lens aperture, or both. While many current cameras have built-in light metering, knowing the light levels surrounding the subject is still useful, especially for studio or portrait photography.
Weather Monitoring: Despite the fact that many light metres are set up for incandescent light, they are nevertheless helpful for making comparisons outside. A metre, for example, may create data indicating the intensity difference between the summer and winter solstices.
Theater Set and Interior Design: Differential light intensities are an efficient means of directing the attention of an audience. A set designer can want a certain piece or character to be shadowed in one scene and emphasised in another. Similarly, an interior designer would employ intensity differences to create a specific appearance and feel.
2. How can the intensity of light be altered?
Ans: The intensity of light decreases as you travel away from a point light source and is proportional to 1/r2, the inverse square of the distance. According to the inverse square law, as light travels twice the distance, its area expands four times as large and its brightness diminishes four times. Hence we can alter the intensity of light by changing the distance.
