Light NOTES.doc

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Pg 3-22

V. LIGHT

A) Electromagnetic Radiation – All forms of energy moving at the speed of light

. . . . All forms of light energy.

1) The difference between all forms of light is wavelength, frequency and photon energy.

 Shorter wavelengths = higher frequency = higher energy

 Longer wavelengths = lower frequency = lower energy 2) Examples of Light: visible, ultra violet (sun burn), infrared

(heat), x-rays, radio

B) Nature of

light - Light acts as having two properties at the same time – wave and particle properties = “wave-particle duality.”

 Particles of light = photons = massless bundles of energy moving @ speed of light.

 Lower energy photons (radio, microwaves, visible) act more like waves.

 Higher energy photons (gamma, x-rays, UV) act more like particles.

(Light.ppt) C) Doppler Effect & Red Shift

 Doppler Effect – The apparent change in a sound’s or light’s wavelength (and frequency) caused by movement toward or away from the source of the sound/light.

 Doppler Effect causes RED SHIFT- apparent movement of light toward the red part of the spectrum.

 RED SHIFT (pg 538, Fig 21.5) occurs when moving objects outside our galaxy, like other galaxies, are observed at different times. An object that is moving away from us will show a shift of its spectral package (all form of light) toward the long wavelength (RED) part of the visible spectrum.

 Red Shift is the strongest piece of evidence for an expanding universe.

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III. LIGHT

A)Electromagnetic Radiation

http://science.hq.nasa.gov/kids/imagers/ems/ xrays.html

Electromagnetic Spectrum basics (2:55 min):

http://www.youtube.com/watch?v=m7c4-EO7ECE

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V. LIGHT

A) Electromagnetic Radiation

–

All forms of energy moving

at the speed of light

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V. LIGHT

1) The difference among all

forms of light is wavelength,

frequency and photon

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V. LIGHT



Shorter wavelengths =

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V. LIGHT

 Shorter wavelengths = higher

frequency = higher energy



Longer wavelengths =

lower frequency = lower

energy

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V. LIGHT

 Shorter wavelengths = higher frequency = higher energy

 Longer wavelengths = lower frequency = lower energy

2) Examples of Light:

visible,

ultra violet (sun burn),

infrared (heat), x-rays, radio

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2) Examples of Light: visible, ultra violet (sun burn), infrared (heat), x-rays, radio

B) Nature of light

- Light acts

as having two properties at

the same time

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2) Examples of Light: visible, ultra violet (sun burn), infrared (heat), x-rays, radio

B) Nature of light - Light acts as having two properties at the same time –

wave properties and particle

properties = “wave-particle

duality.”

Is light a wave or particle (4 min): http://www.youtube.com/ watch?v=J1yIApZtLos

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B) Nature of light - Light acts as having two properties at the same time – wave and particle properties = “wave-particle duality.”



Particles of light = photons

= massless bundles of

energy moving @ speed of

light.

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B) Nature of light - Light acts as having two properties at the same time – wave and particle properties = “wave-particle duality.”



Lower energy photons

(

radio, microwaves, IR,

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

Higher energy photons

(

gamma, x-rays, UV

) act

more like particles.

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(Light.ppt)

Minute Physics: Einstein’s proof of E=mc2 (2:10): https://www.youtube.com/ watch?v=hW7DW9NIO9M

C) Doppler Effect & Red Shift &

Hubble Constant

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C) Doppler Effect & Red Shift



Doppler Effect

– The

apparent change in a

sound’s or light’s

wavelength (and

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 Doppler Effect –

The apparent change in

a sound’s or light’s wavelength

(and frequency) caused by

movement toward or

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-Visible Light package

from another galaxy

First observation

Later observation

 Doppler Effect causes

RED SHIFT

-

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

RED SHIFT

(pg 583, Fig

21.5) occurs when moving

objects in space are

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 RED SHIFT (pg 538, Fig 21.5) occurs when moving objects in space are observed at different times.

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 RED SHIFT (pg 538, Fig 21.5) occurs when moving

objects in space are observed at different times.

An

object that is moving away from us will

show

a shift

of its spectral

package (all forms of light)

toward the long wavelength

(

RED

) part of the visible

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An object that is moving away from

us will show a shift of its spectral

package (all form of light) toward

the long wavelength (RED) part of

the visible spectrum.



Red Shift

is the strongest

piece of evidence for an

accelerating universe.

Red Shift & Big Bang (4:15):

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Red Shift is the strongest piece of evidence for

an accelerating universe.

Hubble Constant: The

value that indicates the

rate of the expansion of

the universe.

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Hubble Constant: The value that indicates the

rate of the expansion of the universe.

The Hubble Constant can be used to:

A) determine the

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Hubble Constant: The value that indicates the

rate of the expansion of the universe.

The Hubble Constant can be used to:

A) determine the brightness and

masses of stars in nearby galaxies,

B) examine those same properties

in more distant galaxies and

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B) examine those same properties in more distant galaxies

and galaxy clusters,

C) deduce the amount of dark

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B) examine those same properties in more distant galaxies

and galaxy clusters,

C) deduce the amount of dark matter present in the universe,

D)

obtain the scale size of faraway

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C) deduce the amount of dark matter present in the universe,

D) obtain the scale size of faraway galaxy clusters,

E)

and serve as a test for

theoretical cosmological models

.

…..Take notes on this video…..

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