Unit 9 Light and Color

Hyperopia

-far-sided -behind retina -(use converging lens to fix)

How the retina works

When light strikes either the rods or the cones of the retina, it's converted into an electric signal that is relayed to the brain via the optic nerve. The brain then translates the electrical signals into the images a person sees,

Lunar Eclipse

occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the sun, Earth, and moon are aligned (in "syzygy") exactly, or very closely so, with the Earth in the middle.

What makes Blue Mountains blue

the sky is blue, clouds are white, sunsets are red, and distant mountains appear bluish because of light scattering. The earth's atmosphere is composed primarily of nitrogen and oxygen molecules, which are very small. When light strikes those tiny molecules, they vibrate.

Myopia

-near-sided -in front of retina -use diverging lens to fix

blue sky

Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time. ... Also, the surface of Earth has reflected and scattered the light.

Critical Angle

Critical angle is the angle of a diamond that either lets light in or out -the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected Critical Angle -Water= 48 degrees -diamond= 25 degrees -plastic= 40 degrees

Translucency

- it allows light to pass through, but does not necessarily follow Snell's law; the photons can be scattered at either of the two interfaces where there is a change in index of refraction, or internally. In other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. Snell's law (also known as Snell-Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.-

How is a rainbow produced?

-A rainbow is an excellent demonstration of the dispersion of light and one more piece of evidence that visible light is composed of a spectrum of wavelengths, each associated with a distinct color. -To view a rainbow, your back must be to the sun as you look at an approximately 40 degree angle above the ground into a region of the atmosphere with suspended droplets of water or even a light mist. Each individual droplet of water acts as a tiny prism that both disperses the light and reflects it back to your eye. As you sight into the sky, wavelengths of light associated with a specific color arrive at your eye from the collection of droplets. The net effect of the vast array of droplets is that a circular arc of ROYGBIV is seen across the sky. -A collection of suspended water droplets in the atmosphere serves as a refractor of light. The water represents a medium with a different optical density than the surrounding air. Light waves refract when they cross over the boundary from one medium to another. The decrease in speed upon entry of light into a water droplet causes a bending of the path of light towards the normal. And upon exiting the droplet, light speeds up and bends away from the normal. The droplet causes a deviation in the path of light as it enters and exits the drop.

Solar Eclipse

-In reality the Sun is much further away then the Moon, but much larger. -The Moon orbits the Earth once a month, and eclipses happen if it lines up exactly with the Earth and the Sun. -Solar eclipses occur at New Moon, when the Moon is between Earth and the Sun. Lunar eclipses occur at Full Moon, when Earth is between the Sun and the Moon. -Eclipses do not take place every month because the orbits of the Moon and Earth are tilted at an angle. Most of the time, the line- up is not precise enough for an eclipse.

How is a mirage formed?

-Mirages happen when the ground is very hot and the air is cool. The hot ground warms a layer of air just above the ground. When the light moves through the cold air and into the layer of hot air it is refracted (bent). A layer of very warm air near the ground refracts the light from the sky nearly into a U-shaped bend.

Opaque

-The opposite property of translucency is opacity. Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color.

Transparency

-is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snell's Law -Snell's law (also known as Snell-Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.

Index of Refraction

index of refraction n of a material is a dimensionless number that describes how light propagates through that medium. It is defined as. where c is the speed of light in vacuum and v is the phase velocity of light in the medium. formula: n=c/v -n: absolute index of refraction or refractive index -v: speed of light in nev medium -c: 3*10^8

sunsets

During a sunset, the sky changes color from blue to yellow to orange to red. As the light travels through more and more atmosphere, it encounters more and more particles. Blue frequencies are scattered (randomly reflect) over and over again; all that is left for your eyes to observe is the slower frequencies. The lower the sun in the sky, the more blue light is scattered away, so your eye sees the leftovers.

How polarized sunglasses work

Polarized sunglasses cut glare and haze so your eyes are more comfortable and you can see better.Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing glare.

Lights affect on the color of grass

The color of grass leaves (usually green) is mostly due to the absorbance of the other wavelengths of visible light by chlorophyll. Therefore, any differences in gene expression (that ultimately determine phenotype) that affect the concentration of chlorophyll in the leaf will, in turn, affect the color of that leaf. My guess is that, in the absence of light, you could still measure chlorophyll concentration, and assume what the color would be. However, you need transmitted (reflected) light in order to perceive color.

Dark Clouds/White Clouds

White Clouds: Bigger molecules vibrate more slowly, scattering slower frequencies of light. Water droplets in clouds vary in size, so each water droplet scatters a different frequency of light. Mixing all the frequencies of light together generates "white" light, and thus clouds appear white. Dark CLouds: rain clouds are gray instead of white because of their thickness, or height. That is, a cloud gets thicker and denser as it gathers more water droplets and ice crystals — the thicker it gets, the more light it scatters, resulting in less light penetrating all the way through it

What makes the ocean blue and green

blue: -Clear water is colored blue mainly due to absorption of red wavelengths more strongly than blue, an effect even seen in swimming pools. Secondarily there is scattering of blue by the same mechanism that colors the sky blue. -and it reflects the sky color -Blue also travels further through water than light with longer wavelengths greenish: -Sometimes the ocean appears other colors besides blue. For example, the Atlantic off the East Coast of the United States usually appears green. This is due to the presence of algae and plant life. The ocean may appear gray under a cloudy sky or brown when the water contains a lot of sediment, as when a river empties into the sea or after the water has been stirred up by a storm.