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!

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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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Components of Daylight Factor