Bard sets a glass prism on a sunny windowsill. A narrow beam of plain white sunlight goes in one side, and a band of color comes out the other.
Red, orange, yellow, green, blue, violet, in order, out of light that looked colorless. Where did the colors come from?
They did not come from the prism. They came in with the light.
Every wavelength of the visible band arrives together in the white beam: the long-wavelength red end, the short-wavelength violet end, and everything between. Mixed together, they look white.
The prism only spreads the mixture apart, sending each wavelength out along a slightly different path, so the band appears in wavelength order, red through violet.
Here is the test that settles it. Send a beam of one single color into the same prism, and one single color comes out. The prism adds nothing.
So the spectrum out of a prism is evidence about the light, not a trick of the glass: everything in that band was already in the white beam.
The same full band is the visible light section of the electromagnetic spectrum. White light carries the whole visible band at once.
A narrow beam of white flashlight light passes through a prism in a darkened classroom. Ysolde sees a full band of colors on the wall. What does the band show about the flashlight's light?
The prism only spreads apart what arrives.
A full band from red to violet appeared, so every one of those wavelengths arrived in the beam.
The flashlight's white light is a mixture of all the wavelengths of visible light.
Zeno sends a narrow beam of pure red light through the same prism. What appears on the wall?
The prism adds nothing; it only spreads apart what arrives.
Only red wavelengths arrived.
A single red patch. No band of colors appears.
A prism spreads a narrow beam of white light into a full band of colors. What does the band show about white light?
Where do the colors in the prism's band come from?
Zeno says: 'White light contains every wavelength of visible light.' Is Zeno correct?
Which statement about white light is correct?
Amity sends a narrow beam of pure green light through a prism. What appears on the far side?
A cut-glass ornament hanging in Bard's sunny window throws small bands of color onto the wall. What do those bands show about sunlight?