AP Chemistry
WS2-5 Electromagnetic Radiation
On a separate piece of paper, show all your work.
1. The blue color in the sky results from the scattering of sunlight by air molecules. The
blue light has a frequency of about 7.50 x 1014 Hz.
a. Calculate the wavelength, in nm, associated with this radiation.
b. Calculate the energy, in joules, of a single photon associated with this
frequency.
2. When copper is bombarded with high-energy electrons, X-rays are emitted. Calculate
the energy associated with the photons if the wavelength of the X-rays is 0.154 nm.
3. A particular form of EM radiation has a frequency of 8.11 x 1014 Hz.
a. What is its wavelength, in meters?
b. What is its wavelength, in nm?
c. What is the energy, in joules, of one photon of this radiation?
4. When a compound containing cesium ions is heated in a Bunsen burner flame, photons
with an energy of 4.30 x 10–19 J are emitted.
a. Calculate the wavelength of the light emitted, in units of nm.
b. What color is the cesium flame?
5. The wavelength of the green light from a traffic signal is centered at 522 nm.
a. What is the frequency of this radiation?
b. What is the energy of one photon of this light?
6. If your favorite FM station is broadcast at a frequency of 104.9 Mhz, then what is the
wavelength of the station’s signal?
7. A certain atom emits light with a frequency of 5.45 x 1016 Hz.
a. Calculate the wavelength of the light.
b. Is this light visible? If not, what region of the spectrum is it in?
AP Chemistry
WS2-5 Electromagnetic Radiation
Answer Key
1. The blue color in the sky results from the scattering of sunlight by air molecules. The
blue light has a frequency of about 7.50 x 1014 Hz.
a. Calculate the wavelength, in nm, associated with this radiation.
1
  7.50 1014
s
c  
8 m
3.00
10
c
s  4.00 107 m
 
 7.50 1014 1
s
4.00 107 m 110 9 nm
 400.nm
1m


b. Calculate the energy, in joules, of a single photon associated with this
frequency.
1
E  h  (6.626 1034 J  s)(7.50 1014 )
s
19
 4.97 10 J
2. When copper is bombarded with high-energy electrons, X-rays are emitted. Calculate
the energy associated with the photons if the wavelength of the X-rays is 0.154 nm.
  0.154nm
0.154nm
E

hc


1m
 1.54 1010 m
9
110 nm
(6.626 1034 J  s)(3.00 10 8
1.54 1010 m
m
)
s  1.26 1015 Hz
AP Chemistry
WS2-5 Electromagnetic Radiation
3. A particular form of EM radiation has a frequency of 8.11 x 1014 Hz.
a. What is its wavelength, in meters?
1
  8.111014
s
c  
m
3.00 10 8
c
s  3.70 107 m
 
1
 8.111014
s


b. What is its wavelength, in nm?
3.70 107 m 110 9 nm
 370.nm
1m
c. What is the energy, in joules, of one photon of this radiation?
1
E  h  (6.626 1034 J  s)(8.111014 )
s
19
 5.37 10 J
4. When a compound containing cesium ions is heated in a Bunsen burner flame, photons
with an energy of 4.30 x 10–19 J are emitted.
a. Calculate the wavelength of the light emitted, in units of nm.

E  4.30 1019 J
hc
E

m
(6.626 1034 J  s)(3.00 10 8 )
hc
s  4.62 107 m


E
4.30 1019 J
4.62 107 m 110 9 nm
 462nm
1m
b. What color is the cesium flame?
Blue

AP Chemistry
WS2-5 Electromagnetic Radiation
5. The wavelength of the green light from a traffic signal is centered at 522 nm.
d. What is the frequency of this radiation?
  522nm
522nm
1m
 5.22 107 m
9
110 nm
c  
m
s  5.75 1014 Hz
 
 5.22 107 m
c


3.00 10 8
e. What is the energy of one photon of this light?
1
E  h  (6.626 1034 J  s)(5.75 1014 )
s
19
 3.8110 J
6. If your favorite FM station is broadcast at a frequency of 104.9 Mhz, then what is the
wavelength of the station’s signal?
  104.9MHz
104.9MHz 110 6 Hz
 1.049 10 8 Hz
1MHz
c  
m
c
s  2.860m
 
 1.049 10 8 1
s
3.00 10 8
7. A certain atom emits light with a frequency of 5.45 x 1016 Hz.
a. Calculate the wavelength of the light.
1
  5.45 1016

s
c  
m
3.00 10 8
c
s  5.50 109 m
 
 5.45 1016 1
s
b. Is this light visible? If not, what region of the spectrum is it in?
No. It’s in the UV region of the EM spectrum.
