Why is there a peak in the visible range?

  • Thread starter MathewsMD
  • Start date
  • #1
433
7

Main Question or Discussion Point

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?
 

Answers and Replies

  • #2
phyzguy
Science Advisor
4,394
1,369
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
D H
Staff Emeritus
Science Advisor
Insights Author
15,393
683
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.
 

Related Threads on Why is there a peak in the visible range?

  • Last Post
Replies
2
Views
1K
Replies
6
Views
1K
Replies
4
Views
1K
Replies
3
Views
617
Replies
1
Views
1K
  • Last Post
Replies
7
Views
4K
  • Last Post
Replies
3
Views
2K
Replies
4
Views
5K
  • Last Post
Replies
0
Views
837
Top