Dispersion, scattering, interference, and diffraction are the main ways that light interacts with matter as it travels. Dispersion occurs when light refracts as it passes through materials like water droplets, causing white light to separate into the colors of the visible spectrum. Scattering redirects light's path and is responsible for the blue color of skies and red-orange hues of sunrises and sunsets. Interference results from the combination of light waves, producing reinforced or canceled out waves that result in iridescent colors. Diffraction causes light to bend and spread around obstacles, making shadows appear fuzzy at the edges.

2. 1. Dispersion of Light
 It happens when light is refracted by particles
acting like another medium (aside from air).
Water for example can disperse light (break it
to different colors) by serving as a second
medium that refracts light.
 The splitting of white light into its constituent
colors is called dispersion. The band of colors
produced is called spectrum. The name ROY
G. BIV is an easy mnemonic for remembering
the colors in this spectrum..

3. A rainbow, nature’s spectacular display of
dispersion of light, is formed when
sunlight passes through the water
droplets suspended in air after a rain
shower. It was Rene Descartes who first
gave a detailed explanation of the
formation of a rainbow by
mathematically tracing the path of light
in a spherical drop of water in1637.

4. a. On entering a water droplet at point A,
part of the light is refracted. The droplet
of water, acting like a mini prism, also
disperses the light. Violet is deviated the
most, red the least.
b. Upon hitting the back surface of the
droplets, light is reflected internally,
obeying the laws of reflection.
c. When it exits the water-air interface,
the light is refracted again and dispersed.

5. 2. Scattering of Light
 Scattering occurs when the particles interact with
white light, causing the latter to be redirected from
its original path.
 a. Rayleigh Scattering
 Named after Lord Rayleigh (John William Strutt),
Rayleigh scattering occurs when the scattering
particles are small compared to the wavelength of
light interacting with it.

6.  Rayleigh scattering accounts for the blue skies and
red-orange sunrise and sunset. When sunlight
enters the atmosphere, the violet and the blue light
are scattered the most. However, our eyes are more
sensitive to blue than violet light and, thus, the skies
appear blue.
 At sunrise or sunset, sunlight travels farther through
the atmosphere. The longer distance would mean
much of the blue wavelengths or shorter
wavelengths have been scattered, leaving only the
longer wavelengths (yellow, orange, and red) to be
scattered. Thus, we have an orange-red sunrise or
sunset.

7. b. Mei Scattering
 Mie scattering occurs when the particles are of the same
size as wavelength of light being scattered. Dust, pollen,
water vapor, and smoke are common Mie scattering
particles. Mie scattering normally occurs in the lower
portion of the atmosphere.
c. Nonselective Scattering
 This type of scattering happens when the particles are
much larger than the wavelength of light. Common
particles responsible for nonselective scattering are
water droplets and large dust particles. All wavelengths
are scattered almost equally, causing fog and clouds to
appear white.

8. 3. Interference
 Perhaps you have noticed the spectrum of colors
reflected from a soap bubble, from an oil slick or
gasoline on a wet road, from a compact disc, from
silvery scales of some fishes, from the eye of a
peacock feather, and from abalone shells and
capiz. All these colors are produced by interference
of light.
 Interference is simply the combination of waves.
The resultant wave is when two or more waves in
accordance with the superposition principle.

9.  Constructive interference results when the
waves arrive together at a point in a phase that
is crest to crest or trough to trough. The result
is a reinforced wave of amplitude equal to the
sum of the amplitudes of the two waves.
 Destructive interference results when the
waves arrive together at a point 1800 out of
phase that is a crest to trough.

10. 4. Diffraction
 Diffraction is the bending of light around an
obstacle and subsequent spreading of light
waves into the region behind the obstacle.
The obstacle may be a slit, wire, hole,
strands of hair, feathers, strings, or straight
edge and the like.
 These obstacles illuminated by a beam of
monochromatic light from a point source
will cast shadows that are fuzzy at the edges.