Transcript QntmEx
ATOMIC THEORY “The Quantum Atom” These spectra came from excited gaseous samples of hydrogen. The BALMER SERIES is the visible spectrum series of emission lines for the hydrogen atom. These lines are the result of electron transitions from: [n = 3 to shell 2] red, [n = 4 to n = 2] blue green, [n = 5 to n = 2] blue, [n = 6 to n = 2] violet, all ending in n = 2 energy level. These transitions can be modeled as follows. Bohr’s revolutionary model of the atom was therefore one with a positive nucleus and “fixed energy” or quantum orbits for electrons. For many years people have wondered just what the Northern Lights are . The Northern Lights or Auroras are, the Creator GodΥs light shows. They fill people with wonder, have inspired artists and poets, and declared GodΥs glory and handy work in the sky and firmament above. More scientific explanations of this phenom enon could not be given until modern particle physic s was developed and knowledge about the EarthΥs magnetosphere probed from satellites. The Sun throws out pa rticles, from its surface, far out into space calle Solar Winds. Σ These play an impo rtant role in causing the Northern light s. What was once hydrog en gas b ecomes a gas o f free electrons and proton s called plasma. This plasma escapes from the SunΥs atmosphere through a hol e in the SunΥs magnetic field. As they escape, th ey are thrown out by the rotation of the sun in a continuous spi ral like water droplets from a garden-ho se. Most of the northern lights we see form in the ionosphe re. The energy of solar wind is converted to vis ible light by a mechanism called a quantum leap. To explain a quantum leap, imagine a hydrogen atom consisting of a single positive proton nucleus around which spins a single elec tron at a set distance. Normally, the elec tron is in an orbit as clo se to the proton as possible. In a state like this, the hydrogen electron has minimum energy . There are other possible orbits further away from the nucleus in wh ich the electron can spin. When a free sub-atomic particle from the solar wind collides with a hydrogen electron at a high speed, it releases energy. Because of this, the spinning electron moves into another, higher energy orbit further out from the nucleus. It now contains more potential energy, but is unstable and unable to keep this energy. It returns to its original orbit, releasing the extra energy as a photon of light. Billions of these quantum leaps that keep occurring create the Northern lights. CChhaarrggeedd ppaarrttiicclleess iinn ssppaaccee tthhaatt ggeett nneeaarr tthhee EEaarrtthh''ss m maaggnneettiicc ffiieelldd ccaann ggeett iinn aanndd ttrraappppeedd.. O Onnccee tthheeyy aarree ttrraappppeedd,, tthhee ppaarrttiicclleess ssppiirraall ddoow wnn tthhee m maaggnneettiicc ffiieelldd lliinnee ttoow waarrddss tthhee EEaarrtthh''ss m maaggnneettiicc ppoolleess.. IItt iiss hheerree aatt tthhee ppoolleess w whheerree tthhee ppaarrttiicclleess hhiitt tthhee ggaasseess iinn tthhee EEaarrtthh''ss aattm moosspphheerree.. TThheessee ccoolllliissiioonnss ggiivvee ooff eenneerrggyy tthhaatt w wee sseeee aass ccoolloorreedd lliigghhtt.. The gases in the Earth’s atmosphere determine the auroral lights’ colors. In the ionosphere, where the collisions are taking place, incoming solar particles collide with oxygen and nitrogen gases. Oxygen atoms give off green and red light. Nitrogen atoms give off red light. Some blue and violet light is also given off, but it is difficult for our eyes to see it. EARTH'S AURORAS MAKE RARE JOINT APPEARANCE • • Scientists using NASA's Polar spacecraft have captured the first-ever movie of auroras dancing simultaneously around both of Earth's polar regions. During a space weather storm on October 22, Polar's Visible Imaging System observed the aurora borealis and aurora australis (northern and southern lights) expanding and brightening in parallel at opposite ends of the world. The images confirm the three-century old theory that auroras in the northern and southern hemispheres are nearly mirror images -- conjugates - of each other. "This is the first time that we have seen both auroral ovals simultaneously with such clarity," says Dr. Nicola Fox, the science operations manager for the Polar spacecraft, based at NASA Goddard Space Flight Center. "With these images, we have the ability to see the dynamics of conjugate auroras." FIREWORK S COLOUR •The colour of light we see depends upon the wavelengths of the electromagnetic radiation. •The visible spectrum contains red, orange, yellow, green, blue, and violet. Low-energy, longer wavelengths are at the red end of the spectrum and Highenergy, shorter ones are at the violet end. •All colours together produce white light. LIGHT Light is emitted by: • Incandescence • Atomic Emissions • Molecular Emissions Incandescence This kind of light is also known as white light . • Incandescent light is created when solid materials are heated to high temperatures, thus creating light. • Explosions with gold or white colours often result from reacting metal shavings in a high temperature environment. Atomic & Molecular emissions These emissions create brilliant colour bursts. •Atomic Emissions: When light is emitted by atoms of an element in the gaseous phase each element has unique colour. •The high temperature environment that is generated when a shell explodes causes electrons to jump to higher energy levels in atoms. •When these “excited” electrons fall back to a lower energy level they emit light of particular colours or wavelengths. •Molecular Emissions: can produce similar effects but are results of molecules instead of elements. Creating Colour In order to achieve these different colours, Pyrotechnicians must add different elements (salts) to the fireworks. • Reds use Strontium and Lithium salts • Yellows & Oranges use Sodium salts • Blues & Purples use copper containing chloride salts, & strontium. These are the most difficult colours to achieve. • Greens use Barium salts Visible Spectrum • Brilliant colours that are seen in an emission spectrum are: • Atomic: When light is emitted by atoms of an element in the gaseous phase. Each element has unique colour. – The excited state environment that is generated when either heat or electric energy causes electrons to jump to higher energy levels in atoms. – When these “excited” electrons fall back to a lower energy level they emit light of particular colours or wavelengths of ‘fixed energy”. • Bohr’s model of the atom was therefore one with a positive nucleus and “fixed energy” orbits for electrons.