Transcript LIGHT, ATOMS, AND TELESCOPES

CH. 4


Energy that can travel through space from one point to
another without any physical link
We can see stars explode, but why can’t we hear them?
 Model
A
• Light is a wave that is a mix of electric and
magnetic energy
 Model
B
• Stream of particles called photons
 Photons - packets of energy
• Electrons & protons move in straight line that can
act like waves
 Wave
– Particle Duality
• Scientists use which ever model the best fits a
particular situation
• Ex. Light reflecting off mirror (model B - photons)
• Ex. Light focusing through a lens (model A - waves)
 Brightness
• Measures the amount of energy carried by the light
 Height of wave (wave model)
 Number of photons (particle model)
 Color
• Visible portion of the electromagnetic spectrum
• Determine light’s wavelength ()
 Red = long , Blue = short 
• White light: Mix of all colors discovered by Newton
with a prism and lens
 Electromagnetic
(EM) Spectrum
All the different lights
 Electromagnetic
Spectrum
• Spectrum of all different types of
electromagnetic waves
 Use
different waves to see what’s going
on in space besides just visible light.
• Radio Waves – longest 
 Use every day – radio telescopes
• Infrared – longer  than visible light
 Can’t see it, but feel as heat
• UV Light – shorter  than visible light
 Infrared
light is the
Light that we perceive
as heat.
 Almost
everything
Gives off Radio light.
Including you. Very low
Energy light.
A
slightly higher energy light that can
interact with different substances and
give them, different visible colors.
Visible Light
UV - Saturn
UV - Rings
E
= hc/
• E = energy
• h = constant
• c = speed of light (constant)
•  = wavelength
 Means:
• Shorter the wavelength, the higher the energy
 As
object’s temp. increases:
• Radiates light more strongly at shorter 
• Color changes:
 Red (long ), Yellow (medium ), Blue (short )
• Allows astronomers to predict temp. of stars
 Black
Bodies
• Objects that absorb all radiation
• Reflect no light and looks black when cold
 See
colors due to excited electrons
• Absorption
 Atoms gain energy exciting electrons to higher
energy levels
• Emission
 Atoms lose that energy and emit a specific color of
light
 Astronomers
use spectrums to study star
composition
• Absorption Spectrum – shows λ of light
absorbed
• Emission Spectrum – shows λ of light emitted
• Each λ of light that is absorbed or emitted can
be match to a specific element
EMMISION SPECTRUM
ABSORPTION SPECTRUM
 Change
from us
in  caused by motion towards or away
 Used
to find/measure speed and direction of
objects
• Ex. Sirens
 Red
Shift
 Blue
Shift
•  appears to increase - Object is moving away
•  appears to shorten - Object is moving closer