What is Reflection Factor?
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Different objects reflect the light in different ways. For example, diffuse surfaces appear the same when viewed from different directions, whereas a mirror looks very different from different points of view!
Must Read: Aims of Good Lighting in a House
Courtesy - 123rf
Reflection factor is a ratio of luminous flux reflected by a body (with or without diffusion) to the flux it receives .i.e.
Reflection factor = luminous flux reflected by a body / luminous flux received by the body
OR
The ratio of the total amount of radiation, as of light, reflected by a surface to the total amount of radiation incident on the surface.
In other words, it is the fraction of radiant energy that is reflected from a surface.
Some symbols used for reflection factor are:
rc= Reflection factor of ceiling.
rw = Reflection factor of parts of the wall between the working surface and the luminaires.
rf= Reflection factor of floor.
Light reflecting factors of commonly used materials:
| Material | Reflection Factor (%) |
| Aluminum, pure, highly polished | 80 – 87 |
| Aluminum, anodised, matt | 80 – 85 |
| Aluminum, polished | 65 – 75 |
| Aluminum, matt | 55 – 75 |
| Aluminum coatings, matt | 55 – 56 |
| Chrome, polished | 60 – 70 |
| Vitreous Enamel, white | 65 – 75 |
| Lacquer, pure white | 80 – 85 |
| Copper, highly polished | 70 – 75 |
| Nickel, highly polished | 50 – 60 |
| Paper, white | 70 – 80 |
| Silvered mirror, behind glass | 80 – 88 |
| Silver, highly polished | 90 – 92 |
| Oak, light polished | 25 – 35 |
| Granite | 20 – 25 |
| Limestone | 35 – 55 |
| Marble, polished | 30 – 70 |
| Plaster, light | 40 – 45 |
| Plaster, dark | 15 – 25 |
| Sandstone | 20 – 40 |
| Plywood, rough | 25 – 40 |
| Concrete, rough | 20 – 30 |
| Brick, red | 10 – 15 |
| Paint, white | 75 – 85 |
| Paint, medium grey | 25 – 35 |
| Paint, dark blue | 15 – 20 |
| Paint, light green | 45 – 55 |
| Paint, dark green | 15 – 20 |
| Paint, light yellow | 60 – 70 |
| Paint, brown | 20 – 30 |
| Paint, dark red | 15 – 20 |
