Chapter 3.8 Applications of the Quantum Model

Laser Technology• the first laser was produced microwave radiation and was

developed by Charles Townes using ammonia molecules.• The first visible light LASER was developed in 1960 by

Theodore Maiman.• LASER - Light Amplification by Stimulated Emission of

Radiation.• Lasers produce a beam of light that is completely

monochromatic - the light only has one wavelength (colour).

• The beam is mode up of coherent waves. Each photon in line follows the previous one precisely so they act as a continuous wave.

• The beam is made up of coherent waves. Each photon in line follows the previous one precisely so they act as a continuous wave.

• In a laser, the beams are precisely parallel to each other so the beam does not diverge significantly as it travels.

• Lasers in CD’s, DVD players, laser printers and copiers and bar code scanners.

• Medical lasers are used for microsurgery, to illuminate fiber optic tubes and in laser eye surgery to re-shape corneas and attach dislodged retinas.

• A rise in energy level of an electron in an atom requires that a specific photon of energy be absorbed.

• If a photon of exactly that energy were to hit an atom already in an excited state the electron would be stimulated to drop back to a lower level.

• This drop would emit another photon of exactly the same energy and moving in the same direction.

• If the electrons of many atoms could be moved to a and held there temporarily a single photon would cause a chain reaction and release a huge number of photons.

• All of these photons would have exactly the same wavelength (colour) and would be in phase with each other.

• The creation of a beam of a huge number of photons from one initial photon is why this process is called amplification.

Spectrophotometers:• Devices used to measure light photons electronically.• They allow detection of wavelengths far shorter and far

longer than the human eye can see.• They can be used for both qualitative and quantitative

analysis. • They can measure light of lower intensity than the human eye

can detect so they can be made incredibly sensitive.

Spectrophotometer

Spectrophotometer measuring the difference in light intensity of yellow light before and after entering a sample solution. Usedto measure the absorption and possible concentration of substances in a sample.

X-Rays and MRI’s• X-rays are extremely high energy photons.• Many x-rays will pass completely through the body while

some of them are blocked or absorbed by tissues in the body.• Exposing film to the x-ray photons that pass through the body

a two dimensional shadow of the internal body structure can be obtained.

• Combining the x-ray machine with digital computer technology can produce a three dimensional image of the body this is a CT of CAT scan.

• X-rays can damage tissues and their yearly use must be limited.

CAT Scan

• Magnetic resonance imaging (MRI).• MRI units use very powerful magnets to create powerful

magnetic fields that “spin” hydrogen nuclei in water molecules.

• The spin effect is sensitive to the local environment (different types of tissues).

• Tissues that appear the same in X-rays can be differentiated in an MRI.

• MRI’s are useful in distinguishing cancerous tissues from normal tissue and damaged tissue in the spine.

Magnetic Resonance Imaging

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