Origin of the Universe
&
Types of Spectra
Origins of the Universe
• Universe: All space, matter, and
energy
• The Universe is vast, and is 10-17
billion years old.
• Big Bang Theory: All matter and
energy in the Universe started
out concentrated in a small area
and, after a huge explosion,
matter began to organize itself
into subatomic particles and
atoms (mostly hydrogen and
helium)
After approximately 1 billion years, atoms came
together to form stars and early galaxies.
The Universe has continued expanding and is
expanding today.
EVIDENCE:
1.) Red-shift in spectra of galaxies
2.) Background microwave radiation
coming from all directions in the Universe.
Timeline
Three Types of Spectra
1. Continuous Spectra
• Produced by a glowing, hot, solid OR liquid AND hot,
compressed gases
Three Types of Spectra
2. Bright Line (Emission) Spectra
• Produced by a hot gas.
• When elements are heated, they produce a
characteristic series of colored lines (bright
line/emission spectra).
• This means that the source is sending out only
certain wavelengths of light.
Three Types of Spectra
3. Dark Line (Absorption) Spectra
• Generated when white light passes through a cooler gas
located between the light source and the observer.
Ex: Hot gases in the interior of the Sun emit a continuous
spectrum, but when the radiation passes through the Sun's
cooler atmosphere, absorption occurs.
• The cooler gas absorbs the wavelengths it would emit if it
were glowing. (absorption spectra = photographic
negative of bright line spectra)
• Stars viewed from Earth with a spectroscope all yield
absorption spectra.
Absorption Spectrum of the Sun
Why is Bright Line Spectra Important?
• Scientists can infer which elements are in stars by
studying the electromagnetic spectra they emit.
Interactions between
Electromagnetic Energy and an
Environment
• When electromagnetic energy comes into contact
with a material, the waves interact with the
material.
• The waves may be:
1. Refracted – waves are bent due
to a change in their speed as they
pass from one medium to another.
2. Reflected – a wave may bounce back when it
meets a surface or boundary that does not
absorb the entire wave’s energy.
3. Transmitted – a wave may pass through the
material
4. Absorbed – a wave is taken into the material
Surface Properties and
Absorption
• Color
• Texture
• Good absorbers of electromagnetic waves
are also good radiators
Why don't microwaves pass through the
oven door, but visible light waves can?
Microwaves
Wavelength = 12 cm
The holes on the door are
smaller than the microwaves,
so the microwaves do not see
the holes.
Visible Light
Wavelength = 0.00005 cm
However, visible light waves
are small enough to pass
through the holes on the
door.