Which light penetrates the atmosphere

Although increased temperatures can speed up photosynthesis, too much heat can be detrimental At a certain temperature, enzymes become denatured and lose their shapes. Denatured enzymes no longer speed up chemical reactions and instead slow down photosynthesis. Thus temperature is an important factor in photosynthetic production, both in activating and maintaining the process. This is why there are different optimal temperatures for photosynthesis for different organisms 1.

Turbidity is a lack of water clarity caused by the presence of suspended particles 1. These particles absorb sunlight and can cause light to be reflected off the particles in water.

The more particles present in the water, the less photosynthetically active radiation that will be received by plants and phytoplankton. This loss of sunlight decreases the rate of photosynthesis. If the photosynthetic production is limited, the dissolved oxygen level in the water will decrease In addition, turbidity can cause significant damage to water habitats by absorbing infrared radiation and increasing water temperature above normal levels. Visible light is the only band of light on the spectrum to be considered photosynthetically active.

It has the perfect amount of energy to excite the electrons needed to start photosynthesis and not damage DNA or break bonds. Ultraviolet can not be used for photosynthesis because it has too much energy. This energy breaks the bonds in molecules and can destroy DNA and other important structures in organisms 8. When plants and other photoautotrophs attempt to use UV-A nm for photosynthesis, electron transport efficiency is decreased, which in turn decreases the rate of photosynthesis 6.

On the other side of the spectrum, infrared light does not contain much energy. The insufficient energy does not excite electrons in molecules enough to be used for photosynthesis.

Infrared light is converted to thermal energy instead 8. This angle will vary by latitude and season. The greater the angle of the sun, the more ozone that sunlight must pass through to reach the surface 9.

Cloud cover, air pollution and the hole in the ozone layer all alter the amount of solar radiation that can reach the surface. These factors all cause typical radiation levels to differ. The irradiance will increase from sunrise until noon, and then decrease until sunset Peak solar energy levels received will vary by latitude and season As seen on the graph to the left, the equator has the steepest solar radiation curve, giving it the shortest sunrise and sunset periods.

In addition, the length of day does not vary greatly throughout the year. This occurs because the angle of the sun does not significantly fluctuate over the equator.

A hemisphere tilted toward the sun would reach a similar peak radiation level as the equator, but with more gradual curves, meaning longer sunrises and sunsets. This hemisphere would also have longer days overall. The opposing hemisphere tilted away from the sun would have shorter sunrises and sunsets, as well as shorter periods of daylight Although the daily values do not appear to change, the level of solar radiation received at the poles will slowly shift throughout the year.

Thus different areas of the globe have different typical radiation levels in each season. At the equator, the typical solar radiation is fairly constant year round There are slight fluctuations but no drastic spikes or drops. In the Northern Hemisphere, the radiation increases as the year progresses until it peaks around June or July. The radiation levels then slowly decrease throughout the rest of the year In the Southern Hemisphere, the radiation levels are opposite.

At the beginning of the year, levels are high and then slowly drop to their lowest point around June. After June, they begin to rise again for the rest of the year Ozone is a molecular gas composed of three oxygen atoms O 3. This area is not completely void of ozone, but is instead a patch of atmosphere that possesses a significantly lower level of ozone than normal While the cause of gap is sometimes a subject of debate, studies have shown that ozone is destroyed when it reacts with chlorine, nitrogen, hydrogen, or bromine When these chemicals enter the atmosphere, they can remove the ozone present.

Regardless of its cause, the hole in the ozone layer allows more UV radiation to reach Earth. If the increase in UV radiation becomes excessive, it can be harmful to both terrestrial and aqueous habitats Unusually high or low levels of sunlight can cause problems for both land and water habitats.

Too much ultraviolet light can cause irreversible damage to DNA and important photosynthetic structures, while too much infrared light can cause overheating 1.

While most living cells have adapted and can repair simple damage, increased exposure to UV radiation can cause cells to mutate beyond repair, or to die On cloudy days, or if a previously sunny location becomes shaded, photosynthetic production can be halted.

Not only does this stop oxygen production, but it increases oxygen consumption through plant respiration 1. The decrease in infrared light will also cool the shaded surface or body of water, which in turns cools the surrounding air. When water is exposed to excessive amounts of sunlight, the infrared radiation will heat the water. The warmer a body water is, the faster the rate of evaporation will be. This can reduce water levels and water flow. In addition, warm water can not hold as much dissolved oxygen as cold water.

This means that in warmer water, less dissolved oxygen is available for aquatic organisms Too much infrared light can also cause the enzymes used in photosynthesis to denature, which can slow or halt the photosynthetic process On the other side of the spectrum, radiation can be limited by cloudy days, shade sources or low sun angles.

If radiation from the sun is lower than usual for an extended period of time, photosynthetic production can decrease or be stopped completely.

Without sunlight, phytoplankton and plants will consume oxygen instead of producing it. These conditions can cause dissolved oxygen levels in the water to plummet, potentially causing a fish kill As in water, terrestrial radiation levels can be limited by cloudy weather This is particularly important to plants, as the photosynthetic process and plant physiology in general are dependent on sunlight. Stomata are pores found on the outer layer of plant leaves.

They open in the presence of sunlight and allow water, carbon dioxide, and oxygen to enter the plant These molecules are then used to produce glucose through photosynthesis. On cold, sunless days, stomata close because not enough energy from the sun is being received to continue photosynthesis Too much intense sunlight can also halt the production of photosynthesis, as stomata will close on sunny, hot and dry days to prevent water loss Sunlight can affect more than the opening and closing of plant stomata.

While some plants have specialized proteins that protect them from sunburn, others do not, and intense solar radiation can damage their leaves Plants that are not adapted to full or intense sunlight, such as hostas or rhododendrons, can develop heat stress.

Many plants, including shade plants, are susceptible to leaf scorch, where parts of the plant die due to excessive water loss through transpiration In addition to slowing or halting photosynthesis, heat stress and leaf scorch can make plants more susceptible to disease or insect infestations. How much light does the sun produce? This computer processed image shows the Crab Nebula pulsar below and right of center and the Geminga pulsar above and left of center in the "light" of gamma-rays.

The Crab nebula, shown also in the visible light image, was created by a supernova that brightened the night sky in A. In , astronomers detected the remnant core of that star; a rapidly rotating, magnetic pulsar flashing every 0. Perhaps the most spectacular discovery in gamma-ray astronomy came in the late s and early s. Detectors on board the Vela satellite series, originally military satellites, began to record bursts of gamma-rays -- not from Earth, but from deep space!

Today, these gamma-ray bursts, which happen at least once a day, are seen to last for fractions of a second to minutes, popping off like cosmic flashbulbs from unexpected directions, flickering, and then fading after briefly dominating the gamma-ray sky.

Gamma-ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year lifetime! So far, it appears that all of the bursts we have observed have come from outside the Milky Way Galaxy.

Scientists believe that a gamma-ray burst will occur once every few million years here in the Milky Way, and in fact may occur once every several hundred million years within a few thousand light-years of Earth. This is illustrated in this cartoon below:. All visible light penetrates the atmosphere, most radio light penetrates the atmosphere, and some IR light passes through the atmosphere. In contrast, our atmosphere blocks most ultraviolet light UV and all X-rays and gamma-rays from reaching the surface of Earth.

Because of this, astronomers can only study these kinds of light using detectors mounted on weather balloons, in rockets, or in Earth-orbiting satellites. If you study the transparency of the Earth's atmosphere plot by the European Southern Observatory , you will see that you can represent this idea of windows in a more rigorous way. You can plot how opaque the atmosphere is or equivalently, what percentage of photons are blocked by the atmosphere as a function of wavelength.

Skip to main content. Radio Waves to Gamma-rays Print When I use the term light , you are used to thinking of the light emitted by a bulb that you can sense with your eyes, which we now know consists of many wavelengths colors of light from red to blue. The entire electromagnetic spectrum is presented from the longest wavelengths of light radio waves to the shortest wavelengths of light gamma-rays at the following NASA website: The Electromagnetic Spectrum That site is written at a level appropriate for younger readers, but they do a very good job of summarizing the different regions of the EM spectrum.

If you want to read about each region in more detail, each page has an excellent summary: Radio waves Microwaves Infrared Optical light Ultraviolet X-rays Gamma Rays Notice that the range that corresponds to the visible light we see with our eyes optical range is a very small part of the entire spectrum!

When a burner on an electric stove is turned on low, it emits only heat, which is infrared radiation, but does not glow with visible light. If the burner is set to a higher temperature, it starts to glow a dull red.

At a still-higher setting, it glows a brighter orange-red shorter wavelength. At even higher temperatures, which cannot be reached with ordinary stoves, metal can appear brilliant yellow or even blue-white.

If one star looks red and another looks blue, which one has the higher temperature? Because blue is the shorter-wavelength color, it is the sign of a hotter star. Note that the temperatures we associate with different colors in science are not the same as the ones artists use. Likewise, we commonly see red on faucet or air conditioning controls to indicate hot temperatures and blue to indicate cold temperatures.

We can develop a more precise star thermometer by measuring how much energy a star gives off at each wavelength and by constructing diagrams like Figure 3. The location of the peak or maximum in the power curve of each star can tell us its temperature. The average temperature at the surface of the Sun, which is where the radiation that we see is emitted, turns out to be K. Throughout this text, we use the kelvin or absolute temperature scale. On this scale, water freezes at K and boils at K. All molecular motion ceases at 0 K.

The various temperature scales are described in Units Used in Science. There are stars cooler than the Sun and stars hotter than the Sun. For the Sun, the wavelength at which the maximum energy is emitted is nanometers, which is near the middle of that portion of the electromagnetic spectrum called visible light. Characteristic temperatures of other astronomical objects, and the wavelengths at which they emit most of their power, are listed in Table 1. If the emitted radiation from a red dwarf star has a wavelength of maximum power at nm, what is the temperature of this star, assuming it is a blackbody?

We can also describe our observation that hotter objects radiate more power at all wavelengths in a mathematical form. If we sum up the contributions from all parts of the electromagnetic spectrum, we obtain the total energy emitted by a blackbody. What we usually measure from a large object like a star is the energy flux , the power emitted per square meter.

It turns out that the energy flux from a blackbody at temperature T is proportional to the fourth power of its absolute temperature. This relationship is known as the Stefan-Boltzmann law and can be written in the form of an equation as.

Notice how impressive this result is. Increasing the temperature of a star would have a tremendous effect on the power it radiates. If the Sun, for example, were twice as hot—that is, if it had a temperature of 11, K—it would radiate 2 4 , or 16 times more power than it does now.

Tripling the temperature would raise the power output 81 times. Hot stars really shine away a tremendous amount of energy. While energy flux tells us how much power a star emits per square meter, we would often like to know how much total power is emitted by the star. We can determine that by multiplying the energy flux by the number of square meters on the surface of the star.