What is Reflection Factor?

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
reflection factor-ratio
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
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