The same force of 10 Newtons is applied to your hand through a tile and you won't feel much but if the same force is applied to your hand through a pin, it will be deeply embedded in your flesh. To understand this, an analogy can be drawn with the units of pressure. (The luminous flux of 1 square meter area is 1 lumen, which is 1lux, and the formula is 1lux=1lm/ ㎡ ) When the luminous flux of 1lm is uniformly irradiated on the area of 1㎡, the illuminance on this area is equal to 1lx. The definition of Lux is the luminous flux per unit area. This brings us to another concept related to luminous flux or brightness. We all know from experience when using a torch that if the spot of light is concentrated very small, it looks very bright, whereas if the spot is enlarged, it is not so bright. But to what extent is the surface of a light-receiving object illuminated by light, and how much light is exactly shining on that object? This needs to be measured by i lluminance : the quotient of the luminous flux irradiated on a certain surface unit divided by the area of this surface unit. When light shines on an object, we say that the surface of the object is illuminated. The luminous flux of torches used in everyday life is a few dozen to a couple of hundred lumens, while some high-intensity torches can have a luminous flux of several thousand or even tens of thousands of lumens. The " l umen" here is a unit to measure the total luminous brightness of the light source, and its definition is: the luminous intensity is the amount of light passed by a 1Candela luminous body in a spherical area of one square degree. Torch enthusiasts often ask how many lumens a torch is. With this basic unit of brightness, Candela, we can define other units. If you want to know how bright a 1 Candela is, buy a candle and light it. If you can't understand it after reading it five times, try to understand it in another way: Candela is the Latin term for candle, so t he brightness of a candle is 1 Candela, and a 100 cd LED-Spot is as bright as 100 candles. Candela, like many other units of physics, has an incomprehensible definition: at a standard atmospheric pressure of 101325 Newtons per square metre, an absolute “black body” with an area equal to 1/60 square centimeter (that is, it can absorb all external light without Ideal reflection object), at the solidification temperature of pure platinum (Pt) (about 2042K or 1769☌), the luminous intensity along the vertical direction is 1 Candela (1cd). The most basic of these units is the luminous intensity, Candela, the symbol is cd, which is used to indicate the intensity of the luminous intensity of the light source in one direction. The eye s can see something glowing because they are actually picking up the electromagnetic energy emitted by that thing in the visible wavelength range, and the more energy your eyes pick up, the brighter they feels.īrightness is related to energy, but the power of the bulb does not fully represent brightness. To describe brightness, let's first understand what brightness is. Well, let me explain to you about "light brightness". A 50 watt incandescent light bulb is no brighter than a 10 watt LED torch, so watt is not a unit of brightness. The light bulbs in the house are usually marked with the number of watts, where "W" is a unit of physics, the full name being "watt", a unit of power measurement. The rest of the money is for you to buy your candy ", I always didn't understand, but did as I was told. When I was a child my father always told me: " Go to the store and buy a 10W bulb. Most people have helped their parents buy light bulbs when they were children. Is watt a unit of brightness? The higher the wattage, the brighter the light will be? So, this is the knowledge we need to know to meet the demands of our daily lives. Similarly, when you buy a mobile power bank to charge your phone, you all need to know how many milliamps it has and how many times a rechargeable battery can supply your phone's battery for every full charge so you can plan your time to use your phone during the journey. When you need to buy a torch, you will want to know these things because you need to know which one has the right brightness for you. What do these 3 units of luminance represent? Are there any differences between them? "Candela" : which represents luminous intensity The commonly used units related to brightness in physics are:ġ. To answer this question you need to know something about the physics of luminance units. When you and your friend are walking under a street light at night and he asks you, "How bright is this light?" What would you answer?ĭo you know how bright your torch is when you need to use it when you go out at night? In everyday life, is the brightness of a torch expressed in the same units as other lamps?
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