What is the formula for irradiance?
The SI unit of irradiance is watt per square metre (W/m2 = Wm−2). An alternative unit of measure is the Langley (1 thermochemical calorie per square centimeter or 41,840 J/m2) per unit time. The solar energy industry uses watt-hour per square metre (Wh/m2) per unit time.
How do you calculate irradiance of light?
Light power (mW) was measured with a (power meter) sensor area of 70.89×10-6 (m2). Then the irradiance of this light from UV lamp was calculated by dividing the light power with sensor area to get its irradiance in W/m2.
What is W m2 NM?
The spectral irradiance at any wavelength, Eλ, is in units of watts per square meter per nm (W m-2 nm-1). The value is a measure of the flux per nm at the specified wavelength incident normally onto an element of the surface divided by the area of the surface element in square meters.
What does J m 2 mean?
joule per square metre
The SI unit of radiant exposure is the joule per square metre (J/m2), while that of spectral exposure in frequency is the joule per square metre per hertz (J⋅m−2⋅Hz−1) and that of spectral exposure in wavelength is the joule per square metre per metre (J/m3)—commonly the joule per square metre per nanometre (J⋅m−2⋅nm−1 …
What is the units for irradiance?
Irradiance is a measurement of solar power and is defined as the rate at which solar energy falls onto a surface. The unit of power is the Watt (abbreviated W). In the case of solar irradiance, we usually measure the power per unit area, so irradiance is typically quoted as W/m², that is, Watts per square meter.
How do you calculate WM 2?
So, you do this calculation at each wavelength and then multiply by the amount of energy in each wavelength and add all the wavelengths, and you end up with something like 18% of the total energy in the spectrum. You divide by this fraction and by the area to get total Watts/m2.
How do you calculate illuminance?
The equation of the illuminance, E, of a small light source is E = P/ 4(pie)d^2, where P is the luminous flux (in lumens, lm) of the source and d is its distance from the surface. Suppose the luminous flux of a desk lamp is 1200 lm.
What unit is W m 2?
Watt Per Square Meter (W/m2) is a unit in the category of Energy flux. It is also known as watts per square meter, watt per square metre, watts per square metre, watt/square meter, watt/square metre. This unit is commonly used in the SI unit system.
Is J m3 PA?
How many Pa*m^3 in 1 joules? The answer is 1. Note that rounding errors may occur, so always check the results.
What Does Mg ha 1 mean?
Named units (e.g., July rainfall) are also acceptable. In SI, a tonne (t) equals 103 kg, or 1 Mg and is understood to mean metric ton. When expressing yields or application rates, the term Mg ha-1 is preferred; t ha-1, widely used outside the United States, is acceptable. For a million tonnes, use Tg (not Mt).
What is irradiance angle?
1 Orientation and angle. The amount of irradiance depends on the latitude. The maximum irradiance corresponds to surfaces, tilted at an angle equal to about the latitude minus 10°.
How is UV irradiance calculated?
One of the most common ways to measure UV irradiance is in watts per square meter (W/m²). An irradiance value of 5 watts per square meter, for example, tells us that a total of 5 watts of UV energy are falling across a one square meter area. The higher the irradiance, the higher the UV level.
How is the spectral irradiance related to the wavelength?
The spectral irradiance as a function of photon wavelength (or energy), denoted by F, is the most common way of characterising a light source. It gives the power density at a particular wavelength. The units of spectral irradiance are in Wm -2 µm -1. The Wm -2 term is the power density at the wavelength λ (µm).
What are the units of spectral irradiance in WM-2?
It gives the power density at a particular wavelength. The units of spectral irradiance are in Wm -2 µm -1. The Wm -2 term is the power density at the wavelength λ (µm). Therefore, the m -2 refers to the surface area of the light emitter and the µm -1 refers to the wavelength of interest.
Which is the SI unit of irradiance per square metre?
The SI unit of irradiance is the watt per square metre (W⋅m −2 ). The CGS unit erg per square centimetre per second (erg⋅cm −2 ⋅s −1) is often used in astronomy. Irradiance is often called intensity, but this term is avoided in radiometry where such usage leads to confusion with radiant intensity.
When do you use distance to measure irradiance?
To compare the irradiance of different sources, one must take into account the distance from the source. A 50 cm distance is often used for such measurements. Irradiance is a useful measure for applications where power must be delivered to large areas.