Electromagnetic Spectrum
Bohr’s Model of the Atom
Electromagnetic Spectrum: different
types of energy that travel in waves
•the wave pattern is made of electric
and magnetic fields that can travel
through empty space
•ex: UV rays, microwaves, visible light
•type of energy depends on frequency &
wavelength
• frequency = how often a wave repeats itself in 1s
represented by , measured in Hz
• wavelength = distance between 2 crests or 2 troughs
– represented by  (Greek symbol lamda), measured in meters
– wavelength of visible light is usually measured in nanometers
(nm) = 10-9 m
How are  and  related?
• the shorter the , the higher the  (the more 
the wave contains)
• the longer the , the lower the  (the less 
the wave carries)
• longer  are safe for humans, short  can be
harmful
– this is why radio waves are safe but X-rays are not
Visible Light
High Energy
Low Energy
• continuous spectrum : a spectrum in
which all the wavelengths of light are
represented in an uninterrupted
sequence
• ex: white light, which is real light that we
see
• it’s a bunch of colours smeared together
• line spectrum = distinct colour lines
rather than white light, unique to each
element
• aka discontinuous spectrum
• each of the bands represents one jump
of an electron
Why??
• each element gives off their own distinct
bands of colour
– the bands appear in the sections that correspond
to various elements
Hydrogen
Carbon
The Bohr Model of the Atom
•Electrons travel in orbits
•Orbits are at fixed
distances
•Electrons will
continue on their path
until told to do
otherwise. (Energy)
Elements and their Colours
•e– can become excited
and can “jump” to a higher
shell
•when the E is removed,
the excited e– “falls” back
down to its ground state
and releases its E in the
form of light
• spectroscope = instrument that separates
light into its component bands of colour
• uses a prism or a diffraction grating
• we use them to identify elements contained in
a substance (ex: stars)
• we can also tell if a body in space is moving
towards us or moving away