Luminous flux is a measure of a light source’s brightness in terms of energy emitted. The lumen is the SI unit for measuring luminous flux (lm). It is a measurement of the energy emitted by a light-producing source in the form of visible light. Luminous flux is a common criterion for comparing light bulbs.
Luminous flux is sometimes referred to as luminous power.
| Name | Luminous flux |
| Unit | Lumen (Lu) |
| Symbol | Φv |
| Lux | 1 lux = lumens/m2 |
Table of Contents
The Lumen
The lumen is the standard unit for measuring a light source’s luminous flux. It is a SI unit derived from the candela. It is defined as the luminous flux emitted by an isotropic point source with a luminous intensity of 1 candela into a unit solid angle (1 sr). The unit lumen is thus equal to cd multiplied by sr. The symbol is v and the abbreviation is lm. In terms of radiant power (also known as radiant flux), it is as follows:
Radiant power (watts) x 683 lumens/watt x luminous efficacy = luminous flux in lumens
The luminous flux is the portion of power seen as light by the human eye, and the value 683 lumens/watt is based on the eye’s sensitivity at 555 nm, the highest efficiency of the photopic (daylight) vision curve. At that frequency, the luminous efficacy is one.
Determining the Luminous Flux
It is more difficult to calculate the Luminous Flux from a source that radiates throughout a spectrum. The Spectral Power Distribution for the specific source must be determined. After that, the Luminous Flux at each wavelength, or at regular intervals for continuous spectra, must be calculated. Adding the flux at each wavelength yields the total flux generated by a visible-spectrum source.
A normal incandescent bulb emits a continuous visible spectrum, therefore various intervals must be utilized to calculate the Luminous Flux. It is, however, somewhat easier for sources such as a mercury vapour lamp. Mercury mainly emits light in the form of a line spectrum. It radiates at six primary wavelengths. This makes determining the Luminous Flux of this bulb against the incandescent lamp easier.
In general, determining the luminous flux for oneself is not essential. It is typically assigned to a lamp based on laboratory testing performed throughout the manufacturing process. The Luminous Flux of a 100W incandescent bulb, for example, is roughly 1700 lm.
How strong are 5000 lumens?
We need 5,000 lumens as your primary light source for a 250-square-foot living room, which is comparable to five 100-watt light bulbs, five 23-watt light bulbs, or eight 10-watt light bulbs.
Candela to lumen?
1 candela equals 1 lumen per steradian. When a 1-lumen beam falls on a 1 square meter surface, it produces an illuminance of 1 lux. As a result, 1 lux equals 1 lumen per square meter.
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Summary
To summarize everything in this article, the following are some important points:
- The luminous flux of a light source is a measure of its brightness in terms of energy emitted.
- It is a measurement of the energy emitted in the form of visible light by a light-producing source.
- The luminous flux is the percentage of power that is seen as light by the human eye, and the number 683 lumens/watt is based on the eye’s sensitivity at 555 nm, which is the maximum efficiency of the photopic (daylight) vision curve. The luminous effectiveness at that frequency is one.
Frequently Asked Questions (FAQs)
Some of the frequently asked questions are given below
1. Difference between Luminous flux and radiant flux
Luminous flux is sometimes confused with radiant flux, which is erroneous. The energy measurement of visible light is known as luminous flux, whereas radiant flux is the entire electromagnetic energy emitted by that source of light. Total electromagnetic energy comprises all visible and non-visible radiation emitted by a source. Luminous flux interprets a human eye’s sensitivity by calculating the power of each wavelength contained in light. To characterize the eye’s reaction to each wavelength, a luminous function is employed.
2. What does luminous flux mean in physics?
The strength of visible light generated by a light source or light fitting is measured as luminous flux. It is expressed in lumens (lm). It should be noted that luminous flux only refers to the perceived power of light.
3. Is higher luminous flux better?
Consumers frequently compare the luminous flux of different light bulbs because it offers an indication of the apparent quantity of light produced by the bulb, and a lightbulb with a greater ratio of luminous flux to consumed power is more efficient.
4. How many lumens is a Lux?
Lumens are units of measurement for the total output of visible light from a light source. The more lumens a light fixture emits, the brighter it is. A lux is one lumen per square metre (lux = lumens/m2).
5. Why Lewis structures are important?
Lewis structure is a simplified representation of valence shell electrons.
It depicts the arrangement of electrons around individual atoms in a molecule.
Electrons are shown as “dots” or as a line between two atoms when they are bonded.
Author
Umair Javed
Umair has been working at Whatsinsight since 2020 as a content writer.
He has a Masters degree in Materials Science.
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