The Electromagnetic Spectrum WS

The Electromagnetic Spectrum WS
Name: _______________________________________
Higher Frequency
Lower Frequency
Wavelength () - Units: m, cm, nm
Frequency () - the # of waves that pass a given point in
one second.
Units: Hz, sec-1, waves/sec, 1/sec
The relationship between frequency (f) and wavelength () of a wave is described by the equation
Waves speed = frequency X wavelength OR
c = 
All electromagnetic radiation propagates at a speed of c = 3.00x108 m/sec (approximately 186,000 miles per
second) this is called the speed of light!
When solving problems using c (the speed of light)  MUST be in Hz or sec-1 and  MUST be in meters.
Problems
1. What is the wavelength of radiation with a frequency of 6.24 x l0
13
-1
sec ?
-6
2. What is the frequency of radiation with a wavelength of 2.20 x l0 nm? (1 nm = 10-9m or 109nm=1m)
3. A television relay transmitter operates at a frequency of 927.9 MHz. Calculate the wavelength of the signal
in nanometers. Is this visible light? (1 MHz = 1,000,000 Hz)
How on earth would I know if it is visible light? Read on to find out!!
The Nature of Electromagnetic Radiation
Electromagnetic radiation includes radio signals, microwaves, infrared, visible light, ultraviolet, X-rays, and
gamma rays. One model of electromagnetic radiation is a propagating wave that is partially electric in nature
and partially magnetic in nature. The following diagram is a pictorial description of this model:
electric part of
wave
magnetic part
of wave
direction of
This type of wave is called an electromagnetic wave. propagation
The Electromagnetic Spectrum
The electromagnetic spectrum is an ordered list of all the types of electromagnetic radiation. All
electromagnetic radiation can be described using the wave model or particle model above. The only difference
between each type is the wavelength and frequency of the associated electromagnetic wave. The types of
radiation and their wavelength ranges are shown in the diagram below.
Electromagnetic Spectrum
Wavelength
9
11
5.55 m to 187 m OR (5.55X10 nm to 1.87X10 nm)
8
9
0.187 m to 5.55 m OR (1.87X10 nm to 5.55X10 nm)
7
8
10 mm to 187 mm OR (1X10 nm to 1.87X10 nm)
750 nm to 1,000,000 nm
400 nm to 700 nm
10 nm to 400 nm
Less than 10 nm
Less than 0.001 nm
Type of Electromagnetic Radiation
AM Radio
TV & FM Radio Waves
Microwave
Infrared (IR)
Visible spectrum
Ultraviolet (UV)
X rays
Gamma (γ) rays
Problems (Use the diagrams on the previous page to answer these questions.)
4. What is the difference between an X-ray, light, and a radio wave?
5. Which type of electromagnetic radiation has:
(a) the longest wavelength?
(b) the shortest wavelength?
(c) the highest frequency?
(d) the lowest frequency?
6. What is the approximate range of wavelengths of visible light? Now go back and answer questions #3!
7. What is meant by the statement “Light is the only thing we can see.”?
Electromagnetic Radiation and Energy
Electromagnetic radiation carries energy with it over space. The energy of a photon (a particle of
electromagnetic radiation carrying a quantum of energy) is given by the equation
Energy
= h X frequency OR E = h
The constant h is called Planck's constant, equal to 6.63x10─34 J●sec, a very small number.
Frequency () – must be in Hz or sec-1
Another equation for the energy of a photon is
Energy = h X speed of light
Wavelength
OR
E = hc

Problems
8. If a certain light has 7.18 x l0-19 J of energy what is the frequency, in Hz, of this light?
b. What is the wavelength, in nm, of this light?
9. If the frequency of a certain light is 3.8 x l014 Hz, what is the energy of this light?
10. The energy of a certain light is 3.9 x l0-19 J. What is the wavelength, in nm, of this light? Is it visible?
11. List the types of electromagnetic radiation in order from lowest energy photons to highest energy photons.