(credit: Jason Hollinger) How Light-Dependent Reactions Work Each pigment can absorb different wavelengths of light, which allows the plant to absorb any light that passes through the taller trees. Figure 5.11 Plants that commonly grow in the shade benefit from having a variety of light-absorbing pigments. ![]() Plants on the rainforest floor must be able to absorb any bit of light that comes through, because the taller trees block most of the sunlight ( Figure 5.11). Other organisms grow in competition for light. Some organisms grow underwater where light intensity decreases with depth, and certain wavelengths are absorbed by the water. Not all photosynthetic organisms have full access to sunlight. Many photosynthetic organisms have a mixture of pigments between them, the organism can absorb energy from a wider range of visible-light wavelengths. Each type of pigment can be identified by the specific pattern of wavelengths it absorbs from visible light, which is its absorption spectrum. Other pigment types include chlorophyll b (which absorbs blue and red-orange light) and the carotenoids. Because green is reflected, chlorophyll appears green. Chlorophyll a absorbs wavelengths from either end of the visible spectrum (blue and red), but not from green. Pigments reflect the color of the wavelengths that they cannot absorb.Īll photosynthetic organisms contain a pigment called chlorophyll a, which humans see as the common green color associated with plants. Understanding Pigmentsĭifferent kinds of pigments exist, and each absorbs only certain wavelengths (colors) of visible light. At the other end of the spectrum toward red, the wavelengths are longer and have lower energy. The visible light portion of the electromagnetic spectrum is perceived by the human eye as a rainbow of colors, with violet and blue having shorter wavelengths and, therefore, higher energy. Certain objects, such as a prism or a drop of water, disperse white light to reveal these colors to the human eye. The visible light seen by humans as white light actually exists in a rainbow of colors. In plants, pigment molecules absorb only visible light for photosynthesis. Light energy enters the process of photosynthesis when pigments absorb the light. The higher-energy waves are dangerous to living things for example, X-rays and UV rays can be harmful to humans. The sun emits a broad range of electromagnetic radiation, including X-rays and ultraviolet (UV) rays. To make a rope move in short, tight waves, a person would need to apply significantly more energy. ![]() It takes little effort by a person to move a rope in long, wide waves. This may seem illogical, but think of it in terms of a piece of moving rope. Short, tight waves carry the most energy. The longer the wavelength (or the more stretched out it appears), the less energy is carried. Visible light is one type of energy emitted from the sun.Įach type of electromagnetic radiation has a characteristic range of wavelengths. This radiation exists in different wavelengths, each of which has its own characteristic energy. Figure 5.10 The sun emits energy in the form of electromagnetic radiation. Each wavelength corresponds to a different amount of energy carried. The electromagnetic spectrum is the range of all possible wavelengths of radiation (Figure 5.10). Visible light constitutes only one of many types of electromagnetic radiation emitted from the sun. Figure 5.9 The wavelength of a single wave is the distance between two consecutive points along the wave. Scientists can determine the amount of energy of a wave by measuring its wavelength, the distance between two consecutive, similar points in a series of waves, such as from crest to crest or trough to trough ( Figure 5.9). Humans can see only a fraction of this energy, which is referred to as “visible light.” The manner in which solar energy travels can be described and measured as waves. ![]() The sun emits an enormous amount of electromagnetic radiation (solar energy). Visit this site and click through the animation to view the process of photosynthesis within a leaf.
0 Comments
Leave a Reply. |