Light

Light Notes 

Notes from September 26th, 2012 

Basic Properties 

The spectrum of light is the light from the Sun as it appears when we pass it through a prism or similar device. Isaac Newton first provided insight about light, when he proved colors in a prism come from the light itself. Newton proved that white light is actually a mix of all the colors. 

Wave Properties of Light 

A wave is something that can transmit energy without carrying material along with it. A wavelength is the distance between adjacent peaks and the frequency as the number of times that any piece of the rope moves up and down. We cannot see light moving when it travels. The longer the wavelength of light, the lower its frequency and energy. The speed at which light travels, or 300,000 km/s. The frequency of a wavelength depends on the length of the wavelength. 

Forms of Light 

Visible light is light visible to the human eye. Light with wavelengths somewhat longer than red light is infrared. Radio waves are the longest wave-length. Ultraviolet lights is light with wavelengths shorter than blue light, or beyond the end of the rainbow. Visible light is only a small part of the entire electromagnetic spectrum. 

Matter

Light carries information about matter across the universe. Planets, stars, and galaxies are made of matter. The Greek philosopher Democritus imagined elements came in atoms. 

Atomic Structures 

Atoms are made of protons, neutrons, and electrons. Protons and neutrons are found in the tiny nucleus at the center of the atom. The atomic number is the number of protons in the nucleus. The atomic mass is the number of protons and the number of neutrons. An isotope has the same number of protons as the original atom, but has a different number of neutrons. 

Learning from Light 

Light interacts through emission, absorption, transmission, reflection or scattering. The spectrum of an ordinary (incandescent) light bulb is a rainbow of color. Thin or low-density cloud of gas does not produce continuous spectrum. If a cloud of gas lies between us and a light bulb, we will still see most of the continuous light emitted by the light bulb. Absorption line spectrum- light is absorbed by gas so we don't see some of it. 

Energy Levels in Atoms 

Electrons can have only particular amounts of energy, and not other energies in between. Each transition corresponds to a unique photon energy, frequency, and wavelength. The lowest possible energy is called the ground-state (energy of 0). Each higher level is labeled with extra energy of an electron. Energy level transition means the electron can rise from a low energy level to a higher energy level.