Chapter Three Light Vocabulary

refraction and optical illusion

Optical illusion through the refraction of light causes a distorted view of an object.

microwaves

Radio waves with the shortest wavelengths and the highest frequencies

convex lens

a lens that is thicker in the middle than the edges

concave lens

a lens that is thinner in the middle than at the edges

medium

a substance in what waves can travel

transulent

letting some light through without being completely transparent

speed of light

light traveling through a medium

iris

muscular diaphragm that controls the size of the pupil

cornea

transparent anterior portion of the outer covering of the eye

infrared waves

EM waves that have wavelengths between 700 nanometers and 1 mm

Why does an object appear to be a certain color?

It's a matter of selective absorption and reflection of the varying wavelengths of light. Our eyes and brain work together to interpret the different wavelengths of light as different colors. White light is composed of all possible wavelengths of visible light, and sunlight is very nearly white. Characteristics of various surfaces cause them to reflect or absorb certain wavelengths. The ones that are reflected to our eyes are what determine the color we perceive. To cite just a single example, if a ball is red, it reflects red light and absorbs the other colors. That's why it appears red. The issue is slightly different for a source of light, and the answer speaks to all other things we see and the colors they appear to have.

diffuse reflection

Reflection that occurs when parallel rays of light hit a rough surface and all reflect at different angles

regular reflection

Reflection that occurs when parallel rays of light hit a smooth surface and all reflect at the same angle

refraction of light

When light travels through one medium into another its speed changes

electromagnetic wave

radiation consisting of waves of energy associated with electric and magnetic fields resulting from the acceleration of an electric charge

absorption

(physics) the process in which incident radiated energy is retained without reflection or transmission on passing through a medium

Why is the grass green?

Sunlight gives off UV rays, which plants absorb to turn into energy. This energy is called ATP. In order for photosynthesis to occur, ATP must be present. Because light comprises of all the colors of the Visible Light Spectrum, or Rainbow, all colors EXCEPT green are absorbed into the chlorophyll. Green is the color reflected and transmitted back, and that is why we see green in plants. (There's a whole lot more, but that's the basics).

rainbow

an arc of colored light in the sky caused by refraction of the sun's rays by rain

scattering

an interaction of light with matter that causes light to change its energy, direction of motion, or both

incident beam

beam of light coming toward a surface

illuminated object

is an object that is lit up because light from luminous object is reflected off of it

opaque

not clear

luminous object

object that emits light, as opposed to one that reflects light

prism

A piece of glass that separates white light into colors of the spectrum.

Why is the sky blue?

The atmosphere is the mixture of gas molecules and other materials surrounding the earth. It is made mostly of the gases nitrogen (78%), and oxygen (21%). Argon gas and water (in the form of vapor, droplets and ice crystals) are the next most common things. There are also small amounts of other gases, plus many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans. The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air. However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue. As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.

reflected beam

The beam of light that is reflected off of a surface from the incident beam

surface

a superficial aspect as opposed to the real nature of something

lens

a transparent object that refracts light waves such that they converge or diverge to create an image

transparent

allowing light to pass through; easily recognized or understood; easily seen through or detected

real image

can be projected into a screen because light passes through the image

virtual image

cannot be projected into a screen because light doesn't travel through the image

pupil

contractile aperture in the iris of the eye

radio waves

electromagnetic waves with the longest wavelengths and lowest frequencies

ultraviolet waves

electromagnetic waves with wavelengths from about 400 billionths to 10 billionths of a meter

angle of reflection

the angle between a reflected ray and a line perpendicular to the reflecting surface at the point of incidence

law of reflection

the angle of incidence is equal to the angle of reflection

angle of incidence

the angle that a line makes with a line perpendicular to the surface at the point of incidence

ROYGBV

the colors of visible light Red Orange Yellow Green Blue Violet

Wavelength

the distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave

focal length

the distance between the lens and the focal point

electromagnetic spectrum

the entire frequency range of electromagnetic radiation

gamma ray waves

the highest frequency and shortest wavelength in the spectrum.

retina

the light-sensitive membrane covering the back wall of the eyeball

normal line

the line perpendicular to the surface

visible light waves

the narrow range of wavelengths in the electromagnetic spectrum that humans can see

transmission

the passing of light or other form of energy through matter

reflection

the phenomenon of a propagating wave (light or sound) being thrown back from a surface

focal point

the point at which beams of light cross after going through a lens

x-ray waves

these are waves with higher energy than electromagnetic waves and can pass many materials easily