Physics and the Quantum Mechanical Model

Physics and the Quantum
Mechanical Model
Light and Atomic Spectra
What is Light??
• What do you think light is? Can you describe
• Isaac Newton (1642-1727) thought of light as
consisting of particles.
• By the year 1900, however, most scientists
accepted the idea that light was a wave
Light as a WAVE
• According to the wave model, light consists of
electromagnetic waves.
• Electromagnetic Radiation – includes radio waves,
microwaves, infrared waves, visible light,
ultraviolet waves, x-rays, and gamma rays.
• All light travels at 3.0x108m/s (or _____________)
The Wave Cycle
• Each complete wave cycle has several
important parts
• The amplitude is the wave’s height from the
origin to the crest
• The wavelength (denoted “λ”) is the distance
between crests.
• The frequency (denoted “ν”) is the number of
wave cycles to pass a given point in a specified
amount of time
Wave Cycle
Wavelength and Frequency
• The frequency and wavelength are inversely
related… meaning as one ____________ the
other ____________.
• As the wavelength increases, the frequency
• The product (multiplication) of these two
values ALWAYS equals a constant (c) which is
known as the ______________________.
Mathematical Relationship
c = λν
c = the speed of light (a constant), 3.0x108m/s
(or 3.0x1010cm/s )
λ = wavelength
ν = frequency, units are cycles per second, or
Hertz (Hz)
Inverse Relationship
The Visible Spectrum
• When light passes through a prism, different
wavelengths separate out into their own
different colors.
• This phenomenal spectrum of colors can be
seen in a rainbow.
• These colors you can see are known as the
The Visible Spectrum
Which part of the
visible spectrum has
the shortest
wavelength and the
highest frequency??
Atomic Emission Spectrum
• Each element emits light when excited with
electricity while in its gas/vapor phase.
• The atoms become “excited” when the absorb the
electrical energy, and the “relax” when that
energy is then released again. This release emits
a “spark” of light, unique to that particular
element, known as the Atomic Emission Spectrum.
Atomic Emission Spectrum
• Calculate the wavelength of the yellow light
emitted by a sodium lamp if the frequency of
the radiation is 5.10x1014 Hz (5.10x1014 s-1)
**use Figure 13.10, page 373**
• What is the wavelength of radiation with a
frequency of 1.50x1013s-1? Does this radiation
have a longer or shorter wavelength than red
**use Figure 13.10, page 373**
• What frequency is radiation with a wavelength
of 5.00 x10-6cm? In what region of the
electromagnetic spectrum is this radiation??
*careful with your units!!*
• Read Chapter 13, section 3
(page 372-382)
• Complete (on a separate
sheet to turn in) Page 386,

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