Why is there a peak in the visible range?

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In summary, the intensity of the graph peaks in the visible portion of the spectrum due to the fact that our eyes have evolved to see the light that is most intense in the solar spectrum. This is not always the case, as the peak can shift depending on the temperature and type of radiation source.
  • #1
MathewsMD
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I have always wondered why the intensity of the graph always peaks in the visible portion of spectrum.

http://3.bp.blogspot.com/-fOnjOBanbcw/TqG1dI81fnI/AAAAAAAABpM/mRL5kfi-i_Y/s1600/ThermalRadiation.png

I understand that the graph represents intensity does not continually increase as wavelength approaches 0, but is there any significance or particular reason for the peak on this graph to be around the visible range of wavelength or is it just a coincidence?
 
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Note that as T decreases, the peak moves out of the visible range and into the infrared, so it doesn't "always" peak in the visible range. The radiation from the cosmic microwave background, for example, peaks in the microwave region. The reason the radiation from the sun peaks in the visible range is that our eyes have evolved to see the light that is most intense in the solar spectrum.
 
  • #3
MathewsMD said:
I understand that the graph represents intensity does not continually increase as wavelength approaches 0, but is there any significance or particular reason for the peak on this graph to be around the visible range of wavelength or is it just a coincidence?
We see in the visible range precisely because that's where sunlight is most intense. The eye evolved to take advantage of that peak lighting. Creatures on a planet orbiting a smaller, redder star would most likely see into the near infrared, but may not be able to see violet or blue.
 

1. Why is the visible range the most important range for human perception?

The visible range is the portion of the electromagnetic spectrum that can be detected by the human eye. This range is important because it allows us to see and perceive the world around us. Without the visible range, we would not be able to see colors, shapes, and other visual information that is crucial for our survival and understanding of the environment.

2. What causes the peak in the visible range?

The peak in the visible range is caused by the absorption and reflection of light by the Earth's atmosphere. The Earth's atmosphere is made up of gases and particles that interact with light in different ways. The gases in the atmosphere absorb certain wavelengths of light, while the particles scatter and reflect other wavelengths. This results in a peak in the visible range, where the majority of light is transmitted through the atmosphere and reaches our eyes.

3. How does the peak in the visible range affect the Earth's climate?

The peak in the visible range plays a crucial role in regulating the Earth's climate. The Earth receives energy from the sun in the form of sunlight, which is mostly concentrated in the visible range. This energy is then absorbed by the Earth's surface and re-emitted as heat. The peak in the visible range allows the Earth to absorb and retain just the right amount of energy to maintain a habitable temperature for living organisms.

4. Can the peak in the visible range change over time?

Yes, the peak in the visible range can change over time due to various factors, such as changes in the composition of the Earth's atmosphere, volcanic eruptions, and human activities. For example, the burning of fossil fuels releases pollutants into the atmosphere, which can alter the peak in the visible range and contribute to climate change.

5. How is the peak in the visible range measured and studied?

The peak in the visible range is measured and studied using instruments such as spectrophotometers and satellites. These instruments can detect and measure the intensity of light at different wavelengths, allowing scientists to map out the peak in the visible range and track changes over time. Additionally, scientists use mathematical models and computer simulations to study the impact of the peak in the visible range on the Earth's climate and predict future changes.

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