I've heard that the sky is blue because blue is a shorter wavelength and thus scatters more than longer wavelengths. Why is there a peak between 400-500 nm? Why is the sky not ultraviolet?
mooreyeel
I think the ozone stops the UV rays from coming in, at least most of them. Otherwise all that radiation would kill us. Also I don't think we can see ultraviolet?
ericyche
I'm a bit confused how to interpret the SPD for certain regions. The solar disk,, i was expecting to be a straight horizontal line because white is the prominent color but I guess it also has way more wave lengths outside of visible light.
modatberkeley
I think it's pretty interesting that we've evolved to be able to see the wavelengths of a blue sky.
modatberkeley
I remember learning in physics that higher frequency (lower wavelength) light has higher power -- I guess in figure (b) that effect is not seen because the sun is red-skewed? I might be missing something here...
sberkun
Hmmm, I'm also confused about the Solar disk spectrum shown here. I would expect it to match the "daylight" graph on the next slide, but it matches the "incandescent" graph instead.
Incandescent bulbs and the sun are both blackbodies. This interactive demo shows the spectra of different ideal blackbodies.
william-fei
To calculate white balance, we are supposed to choose a "neutral" part of the image where the reality is equal amounts of red, green, and blue. The algorithm then does matrix multiplication to balance out the rest of the image. Why is it the case that you cannot choose the blown out sun in the sky as your white balance selector? In this image, the sky looks completely white.
alvin-xu-5745
Even though shorter wavelength purple would be scattered more, the sky appearing blue to us is not merely because of more emission in the blue region, but also because of our physiology: our eyes are more sensitive to blue than purple. Even shorter wavelengths are not visible to us and thus we cannot see things like ultraviolet.
I've heard that the sky is blue because blue is a shorter wavelength and thus scatters more than longer wavelengths. Why is there a peak between 400-500 nm? Why is the sky not ultraviolet?
I think the ozone stops the UV rays from coming in, at least most of them. Otherwise all that radiation would kill us. Also I don't think we can see ultraviolet?
I'm a bit confused how to interpret the SPD for certain regions. The solar disk,, i was expecting to be a straight horizontal line because white is the prominent color but I guess it also has way more wave lengths outside of visible light.
I think it's pretty interesting that we've evolved to be able to see the wavelengths of a blue sky.
I remember learning in physics that higher frequency (lower wavelength) light has higher power -- I guess in figure (b) that effect is not seen because the sun is red-skewed? I might be missing something here...
Hmmm, I'm also confused about the Solar disk spectrum shown here. I would expect it to match the "daylight" graph on the next slide, but it matches the "incandescent" graph instead.
Incandescent bulbs and the sun are both blackbodies. This interactive demo shows the spectra of different ideal blackbodies.
To calculate white balance, we are supposed to choose a "neutral" part of the image where the reality is equal amounts of red, green, and blue. The algorithm then does matrix multiplication to balance out the rest of the image. Why is it the case that you cannot choose the blown out sun in the sky as your white balance selector? In this image, the sky looks completely white.
Even though shorter wavelength purple would be scattered more, the sky appearing blue to us is not merely because of more emission in the blue region, but also because of our physiology: our eyes are more sensitive to blue than purple. Even shorter wavelengths are not visible to us and thus we cannot see things like ultraviolet.