10 Feb 24 Eye, Scattering, Fluorescence, Phosphorescence Slideshare

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Published on February 27, 2009

Author: skoch3

Source: slideshare.net

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Human perception of color, fluorescence, applications of fluorescence in biology, why the sky is blue

Today: Perception of color, Fluorescence, Why sky is blue Transgenic mouse glowing because of green fluorescent protein from jellyfish (U. Penn)

Homework Question Thank you Michelle for the pictures with MS Paint! John B. At the time the earth experiences a solar eclipse, the moon observers would see a “lunar eclipse” in where the earth will be almost all light up by the sun, except for the shadow the moon would be casting in the earth. The observers would see the umbra and the penumbra created by the moon on the earth. Melody B. If we were standing on the moon during a solar eclipse we would see a small dark shadow on the Earth. This is because the moon in directly between the sun and Earth, is blocking some of the suns rays to the Earth, and is creating a small umbra with a penumbra around the umbra on the Earth. Analisa A. During a lunar eclipse the Moon people would see the Earth and that is the side of the Earth that is sleeping- the night side. There would also probably be a ring of sunlight around the Earth- like there is around the moon during a solar eclipse (as viewed on Earth). Melody A…during a lunar eclipse, when the sun fell directly behind the Earth, the Earth would look darker and there would be a thin red circle outlining the Earth, where the sunlight would be refractring through the thin atmosphere.

I’ll post some photos later on WebCT. From Veronica http://apod.nasa.gov/apod/ap070302.html Thank you Michelle Cronoble for the pictures with MS Paint!

Our eye has color receptors and B/W receptors (these are sensitive photon detectors) Wikipedia Most people have trichromatic vision color blind = dicrhomatic (still have color perception) some reports of tetrachromatic ! Key concept: the “physics of color” is really due to the anatomy and physiology of our eyes and brains Photon detector

Let’s settle the ROYGBIV issue! Spectral colors are colors that you see from a single frequency of light (monochromatic)…or colors that make up the spectrum e.g., magenta is NOT a spectral color Newton was a little biased in his description of ROYGBIV It actually should be ROYGCBV…cyan IS a spectral color

Demonstrations of perception of light and color Perception of white light Additive primary colors (trichromatic vision) (This is biology!) Subtractive primary colors Cyan, Yellow, Magenta

Perception of white light

Demos – Can you believe your eyes? Bidwell’s disc (this is a tricky one) Color wheel and optical discs

Bidwell’s disc (this is a tricky one)

Color wheel and optical discs

Clicker Question—Spectral colors Which of the following is NOT a spectral color? Reminder: a spectral color is a “pure” color that can be created by a single frequency of light. Magenta Cyan Yellow Blue Green

Which of the following is NOT a spectral color? Reminder: a spectral color is a “pure” color that can be created by a single frequency of light.

Magenta

Cyan

Yellow

Blue

Green

Clicker Question—Spectral colors Which of the following is NOT a spectral color? Reminder: a spectral color is a “pure” color that can be created by a single frequency of light. Magenta is a mixture of blue and red Cyan Yellow Blue Green These CAN be created by mixtures, but also are spectral colors

Which of the following is NOT a spectral color? Reminder: a spectral color is a “pure” color that can be created by a single frequency of light.

Magenta is a mixture of blue and red

Cyan

Yellow

Blue

Green

Fluorescence (1) Molecule absorbs a photon of a certain energy (2) Molecule emits a photon of lower energy (nanoseconds delay)

Fluorescence (1) Molecule absorbs a photon of a certain energy (2) Molecule emits a photon of lower energy (nanoseconds delay) UV Light

Phosphorescence is similar to Fluorescence, but slower UV Light demo…if available

UV Light demo…if available

Clicker Question—Fluorescence Which of the following is a possible kind of fluorescence? One red photon absorbed, one green emitted One red photon absorbed, one blue emitted One infrared photon absorbed, one blue emitted One ultraviolet photon absorbed, one blue emitted One blue photon absorbed, one ultraviolet emitted

Which of the following is a possible kind of fluorescence?

One red photon absorbed, one green emitted

One red photon absorbed, one blue emitted

One infrared photon absorbed, one blue emitted

One ultraviolet photon absorbed, one blue emitted

One blue photon absorbed, one ultraviolet emitted

Clicker Question—Fluorescence Which of the following is a possible kind of fluorescence? One red photon absorbed, one green emitted One red photon absorbed, one blue emitted One infrared photon absorbed, one blue emitted One ultraviolet photon absorbed, one blue emitted One blue photon absorbed, one ultraviolet emitted Conservation of energy! High energy photon absorbed, lower energy emitted.

Which of the following is a possible kind of fluorescence?

One red photon absorbed, one green emitted

One red photon absorbed, one blue emitted

One infrared photon absorbed, one blue emitted

One ultraviolet photon absorbed, one blue emitted

One blue photon absorbed, one ultraviolet emitted

Fluorescence is a very powerful tool in biology A single protein can be “labeled” fluorescently Different colors can label different proteins “ Quantum dots” of various colors Lung epithelial cells (DNA blue, cilia red)

A single protein can be “labeled” fluorescently

Different colors can label different proteins

Fluorescence Microscopy Filters allow blocking the excitation light (so only light comes from fluorescence)

Filters allow blocking the excitation light (so only light comes from fluorescence)

For example, we can see proteins “absorbed” by cells “ Chinese Hamster Ovary” cells, up-taking quantum dots coated with protein Diane Lidke, UNM HSC

“ Chinese Hamster Ovary” cells, up-taking quantum dots coated with protein

Diane Lidke, UNM HSC

There are naturally fluorescent proteins GFP (“Green Fluorescent Protein”) from the jelly fish Osamu Shimomura and Roger Y. Tsien—2008 Nobel Prize, Chemistry Scientists know how to add GFP to the genome of a cell -> ANY protein can be made to glow green! GFP Mouse!

GFP (“Green Fluorescent Protein”) from the jelly fish

Osamu Shimomura and Roger Y. Tsien—2008 Nobel Prize, Chemistry

Scientists know how to add GFP to the genome of a cell

-> ANY protein can be made to glow green!

In addition to being absorbed, light can also be scattered

The atmosphere scatters some sunlight Light (an oscillation) can cause molecules to resonate The closer to the resonant frequency, the more scattering (Imagine the “resonant square” demo…or acoustic resonance) Visible light is below the “resonant” frequncey of Nitrogen

Light (an oscillation) can cause molecules to resonate

The closer to the resonant frequency, the more scattering (Imagine the “resonant square” demo…or acoustic resonance)

Visible light is below the “resonant” frequncey of Nitrogen

Clicker Question—Scattering Which of the following is closest to the resonant frequency of a nitrogen molecule? Red light Blue light Green light

Which of the following is closest to the resonant frequency of a nitrogen molecule?

Red light

Blue light

Green light

Clicker Question—Scattering Which of the following is closest to the resonant frequency of a nitrogen molecule? Red light Blue light Green light The intensity of light waves scattered by the atmosphere is higher at higher frequencies Intensity  (frequency) 4

Which of the following is closest to the resonant frequency of a nitrogen molecule?

Red light

Blue light

Green light

So why is the sky blue? Why are sunsets red? Lunar eclipse NASA

The blue sky and red sunsets are the same effect!

Sunset demo

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