Mass Spectrometry – How it works, what it does, and how it ...
What is it? How does it work? How do we use it?. o Electromagnetic Waves display wave behavior o...
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Transcript of What is it? How does it work? How do we use it?. o Electromagnetic Waves display wave behavior o...
http://www.youtube.com/watch?v=DfPeprQ7oGc
o Electromagnetic Waves display wave behavioro Created by oscillating electric and magnetic
fields
o Electromagnetic Spectrum – range of frequencies of EM waves
Dual Nature
o Visible light – the range of EM that produces
light that we can detect
o Radio and Microwaves are produced by placing a magnetic field in an oscillating electric field
o X-rays are produced when fast-moving electrons strike a metal target
o Infrared from the sun is responsible for the heating from the sun
o Gamma rays are emitted during nuclear collisions
EM Spectrum
o Transverse waves
o Nonmechanical
o All EM waves travel at the same speed:o c = m/s
o Example: Red light with a frequency of Hz has what wavelength?
Characteristics
Concave - convergent (all rays come together)
Real focal point (the rays REALLY intersect)
Convex – divergent (all rays spread apart)Virtual focal point (the rays SEEM to intersect
behind the mirror)Produces virtual images only
Mirrors - work by reflection
Convex – convergent Real focal point
Concave – divergent Virtual focal point Produces virtual
images only
Lenses - work by refraction
o Vibrations in a vertical plane – vertical polarization
o Vibrations in a horizontal plane – horizontal polarization
o Polarization only exists for TRANSVERSE waves!!!
Polarization
o We all see color in different ways.
o When light reaches our eyes, we do not see just one frequency, but a variety of frequencies at various intensities.
o For example, white light is NOT a color! o It is the presence of all frequencies of visible
lighto NOT the only way to produce
white light!
o Primary Colors – any three colors
that combine to form white light
Color Perception
o Most common primaries are red, green and blue
o Yellow, magenta, and cyan are secondary colors
o Colors add to form white light
o Colors subtract to form black!
Color Mixing
o Myth –”No one set of colors can produce all other colors”o Almost any three colors can be mixed to
produce the other colors
o Colors can be mixed to get even the primary colors!o They will never be as pure as the original
frequency
o Red, yellow, and blue are not even the best primary set!
Color Mixing - myths
o When light encounters a different substance, part of the light is absorbed while the rest is REFLECTED!
o Texture of a surface determines how much reflection
o For flat mirrors: angle of incidence = angle of reflection
Reflection
𝜃=𝜃 ′
• Light can be approximated as rays!
• Light produces two types of images:• REAL – these appear in front of the mirror on a ray
diagram• In reality, REAL images can be projected onto walls
and screens• VIRTUAL – these appear behind the mirror on a ray
diagram• In reality, VIRTUAL images can only be seen by
looking into the mirror
• Ray diagrams help us predict image location, orientation, similarity, and type of image
(LOST)
Drawing Ray Diagrams – allows us to predict the location of an image
• Draw all rays from the top of the object.
• The radius of curvature is the center of your circle; the focal point is HALF that value.
• Use a ruler and be exact.
• RAY 1: Draw parallel to the principal axis, reflect through the focal point.
• RAY 2: Draw through the focal point, reflect parallel to the principal axis
• RAY 3: Draw through the radius of curvature; reflect back on itself.
• Image appears where the three reflected rays intersect!
Rules (Curved Mirrors):
• f is the focal point of the mirror and is HALF the radius of curvature (it is NEGATIVE for a CONVEX mirror)
• p is object distance from the mirror
• q is image distance from the mirror (it is NEGATIVE for a VIRTUAL image)
• h is object height
• h’ is image height (it is NEGATIVE for INVERTED images)
We can MATHEMATICALLY predict image formation also!!!!
=
o Defined as the bending of light as it travels from one medium to another
o Depends upon the index of refraction of the material…
Refraction
• Index of refraction, n, tells us how fast light travels in the medium• nwater = 1.33 (slower)
• nglass = 1.5 (slowest)
• nair = 1.00 (fastest)
• Tells me how the light will bend:• Fastest to slower, light bends TOWARD
THE NORMAL• Air to water• Slower to faster, light bends AWAY FROM THE
NORMAL• Water to air
Refraction
• Ray 1: Parallel to the principal axis to middle of lens. Refract through BACK focal point.
• Ray 2: Through the FRONT focal point to middle of lens. Refract parallel to principal axis.
• Ray 3: Through lens center.
Lens Ray Diagrams
• Waves spread when they pass through an opening
Diffraction