There a couple things that must happen to all wavelengths of light so that a substance can reflect white. The substance needs to be able to reflect each wavelength equally and the wavelengths must hit it at the same time.
All wavelengths of light must be absorbed by the substance for it to appear black. When no light is reflected or transmitted, the substance appears black because no color is perceived by the human eye.
must be reflected
For a substance to appear white, all wavelengths of light must be reflected equally and simultaneously. This results in a balanced mixture of all visible colors being reflected off the surface.
A substance that appears black (in a lighted room) is absorbing all of the visible light that hits it, leaving no visible light to reflect off of it to your eye. So it's absorbing visible light of all wavelengths. (You still don't know what's happening to the infra-red or ultraviolet hitting it. For that, you need to use different detectors.)
When a substance appears white, it means that all wavelengths of visible light are being reflected equally by the surface of the substance. This results in a combination of all colors of light reaching our eyes, which our brain interprets as white.
All wavelengths of light must be absorbed by the substance for it to appear black. When no light is reflected or transmitted, the substance appears black because no color is perceived by the human eye.
must be reflected
For a substance to appear white, all wavelengths of light must be reflected equally and simultaneously. This results in a balanced mixture of all visible colors being reflected off the surface.
A substance that appears black (in a lighted room) is absorbing all of the visible light that hits it, leaving no visible light to reflect off of it to your eye. So it's absorbing visible light of all wavelengths. (You still don't know what's happening to the infra-red or ultraviolet hitting it. For that, you need to use different detectors.)
When a substance appears white, it means that all wavelengths of visible light are being reflected equally by the surface of the substance. This results in a combination of all colors of light reaching our eyes, which our brain interprets as white.
A substance that appears black (in a lighted room) is absorbing all of the visible light that hits it, leaving no visible light to reflect off of it to your eye. So it's absorbing visible light of all wavelengths. (You still don't know what's happening to the infra-red or ultraviolet hitting it. For that, you need to use different detectors.)
Light comes in many different "wavelengths". The wavelength of a beam of light determines its color.White light contains light of all different wavelengths, but objects can reflect of absorb different wavelengths.The light that an object reflects determines its color.In other words, an object that looks red must be absorbing all wavelengths of light except red.
The colours we see in an object are only the colours that are reflected. Inferentially, the other colours are absorbed. The grass is green (when illuminated by a white light source) because the redder end of the spectrum is absorbed and used by the plant to do its stuff - photosynthesis and so on. A white card appears white because all the light wavelengths [to which we can respond] are reflected. That card may absorb some of the white light, but not at wavelengths to which we respond.
All of the wavelengths of VISIBLE LIGHT.
All of the electromagnetic spectrum can be reflected. White light is a combination of all colors. They all reflect, red is among them.
Black is seen when all wavelengths of light are absorbed because no light is reflected back to the eyes.
must be reflected