UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
How it Works
Ask a Question
Search Topics
Our Scientists
Science Links
Contact Information
Why do some things reflect your image (like metall or dark window glass) and other things do not (like wood, concrete, paper)?
Question Date: 2005-10-05
Answer 1:

Everything that is not "luminous" itself, that is, does not produce its own light, does reflect light - or you would not see it! So, if everything reflects light, then why don't you see an image?Because only very, very smooth surfaces reflect light rays parallel to each other, so that you get an image. This is called "specular"reflection, which means "mirror-like" (from the Latin word speculum, meaning "mirror"). Every surface that is not smooth like metal or glass reflects light in all different directions, so that the light gets scattered. We call that "diffuse" reflection. Then you just see the object itself, because it reflects light, but the scattered rays that go off in all different directions cannot produce an image.

Answer 2:

Smooth surfaces reflect light, and rough surfaces do not. Because of the nature of the substances, it is impossible to make wood, concrete, paper, and the like smooth enough to reflect coherent images, but it is possible to make metals, crystals, liquids, etc. sufficiently smooth.

Answer 3:

This is actually not a simple question to answer. Things reflect because of a combination of things, including their refractive index, how smooth the surface is, and finally, in the case of metals, and mirrors, because there are electrons in the material that are free. Consider that a shallow pool of water will reflect, but the ocean does not usually reflect, particularly if there are waves on it. One reason that things reflect is that the speed at which light travels changes depending on whether it is traveling in air, water etc. and when it goes from air to water, some of the light is bounces off, which causes reflections. The scientific term for this is refraction, and water has a higher refractive index than air. Wood, concrete and paper don't reflect, partly because their surfaces are not very smooth, and he light that hits the surface of these materials is scattered all over. A smooth sheet of paper (a glossy magazine cover) will reflect.

Answer 4:

I'm a geologist so I like your question! Let's start by talking about what a mineral is. A mineral is an inorganic (was never alive) substance with a specific chemical composition and atomic structure.
The atoms of some minerals are arranged in such a way that the mineral has a shiny or metallic luster. The word luster is used to describe the way a mineral's surface reflects light. Be careful, though! Some surfaces are shiny because we polish them and not because they look that way naturally.
Glass is naturally shiny because it is composed of the mineral quartz (very common in beach sand) which has a shiny luster. Concrete is made up of pebbles and a matrix of clayey material.
Although some of the individual pebbles might be shiny, the clay minerals all around them and covering them are dull. Wood and paper are in a completely different category because they were once alive and are considered organic.

Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use