Physical Science Light
White Light • The light coming from the sun is what we call white light or a mixture of all colors • Can be separated into it components with a prism
Addition of Light • Blue and red = magenta (purplish color) • Green and blue = cyan (greenish blue) • Red and green = yellow
Mixing of Colors in Pigments • Mixing of light different than mixing pigments • When you mix paint, you mix small particles that absorb the complimentary color.
Mixing of Colors in Pigments • The small particles in the pigment absorb specific colors and thus we see what is not absorbed. • For instance, a paint that looks red has small particles in it that absorb cyan and thus reflects its complimentary color red.
Diffraction Bending of light (waves) by means other than reflection of refraction
Why is the Sky Blue • Recall the tuning fork demo – one vibrating fork causes another to vibrate • When light waves strike atoms in the atmosphere they cause them to scatter light (reemitted light in all directions)
Why is the Sky Blue • The nitrogen a oxygen primarily scatter violet light • Our eyes are not as sensitive to violet light so we see it mostly as blue
Why is the Sky Blue • Water vapor effects the color – dry air – really blue • Particles in the air tend to turn it grey or brown • After a good rain, the sky seems deeper blue
Why are sunsets red? • Light that isn’t scattered is transmitted through the air • Red light is scattered the least and therefore transmitted the best • The further light travels through the atmosphere, the more opportunity to be scattered
Why are sunsets red? • If light passes a long way, more of the high frequency (blue) light is scattered and red becomes more predominate. • When we look toward the sun at sunrise or sunset, we se light traveling through a lot of atmosphere • So red is the predominate color to reach our eyes.
Why are clouds white • Clouds contain clusters of water droplets in various sizes • Different sized water clusters scatter light at different frequencies • We see different frequencies as different colors • If you have clusters producing red, green and blue – we see white
Why are clouds white • Clouds also contain a large quantity of free electrons • These electrons vibrating in step increase the intensity of the light therefore clouds tend to be bright
Why are clouds white • As the water droplets get larger they absorb more of the light so clouds become darker just prior to raining.