Here,we are going to give you a quick review of what is light transmittance of glass,and how to obtain higher light transmittance.
Usually,there are three performances when the light shine on the glass surface,they are:Reflection, Absorption and Transmission:
- The light goes through the glass, known as “transmissive”,which is expressed in terms of “light transmittance”.
- The part of Light is blocked by the glass, and reflected by a certain angle, called “reflection”, it is expressed in terms of “reflectivity”.
- After the Light goes through the glass body, some part of the light energy is lost, known as “absorption”, expressed in terms of “absorption rate”.
light transmittance of Glass is a percentage of expression,it depends on the amount of the glass light that passed the glass and the total light amount that shine on the glass.
Reflectivity + Absorbance + Transmittance = 100%.
The average light transmittance of the ordinary glass is just slightly higher than 80%
(Heat-reflective glass:which is used for shading and heat insulation,that largely requiring high reflectivity)
Analysis of the glass light transmission loss:
The relationship between light transmittance (T), reflectance (R) and absorbance (A). According to the law of the energy conservation:when light passes through any medium that has the following relationship:
T + R + A = 1
How to obtain higher light transmittance:
In order to obtain a higher light transmittance, it should reduce the light reflection on the glass surface,the light absorption
- Reflectance increases by the light incident angle, but the reflectivity changes little when the angle is less than 40 degrees.but when the angle is larger than 70. The reflectivity increases sharply with increasing incident angle.
- The reflectivity also increases as the refractivity difference increases between the medias.but for the glass and air, the air refractive n0 = 1, while the glass refractive n1 = 1.52, the refractive is fixed.so,the reflectivity mainly depends on the light angle.
- Light absorption loss:the deeper the glass color is,the less the transparent will be.In order to reduce the light absorption loss, a lighter color glass is necessary. In addition, the light absorption loss decreases along with the glass thickness decrease.
- Light scattering Loss:generally it occurs in the composite glass, because some of the glass can change the directions of light particles, some of the light can not be imaged and lose its role.
- Other factor that affecting the light transmittance of glass is the smoothness of the glass surface,which could not be neglected.since there may differ by more than 1%.that increase the glass reflectivity and decrease the glass transmittance.
- Impurities in the glass raw material also affect the light transmittance, such as ferric oxide, that is why low iron glass is the better choice if we need higher glass light transmittance.