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Frequency and Energy Problems
l = c/n c= 3.00 X 108
m/s
E = hn h= 6.626 x 10-34
J/Hz 1Hz = 1/s
1) What is the energy of a photon whose frequency is 3.0 X 1012
Hz?
E =[6.626 x 3.0] 10 (-34+12) J
2) Calculate n for a l
= 700 nm. n = c/l nm =
nanometers
Calculate n for a
l = 400 nm. n = c/l
nm = nanometers
Calculate the energy for each wavelength.
Which wavelength has the greatest frequency? Which
wavelength has more energy?
Red 700nm
n = 4.3 x 1014 /s
or 4.3 x 1014 Hz
Blue 400 nm
n = 7.5 x 1014 /s
or 7.5 x 1014 Hz
Red
E = 2.8 x 10-19 J
Blue
E = 5.0 x 10-19 J
Blue, 400 nm, has the
greatest frequency and the greatest energy.
3) A red light has a wavelength of 728 nm.
What is the frequency of the light?
What is the speed of the wave in m/s?
n = 4.12 x 1014 /s
or 4.12 x 1014 Hz
speed = wavelength x
frequency
speed = 2.99 x 108 m/s
4) A purple light has a frequency of 7.42 x 1014 Hz.
What is its wavelength in nm?
What is the energy of one quanta of light.
l =
404 nm
E = 4.91 x 10-19
J
5) You broke your big toe! The x ray they take of toe uses waves
that have a length
2.19 x 1010m.
What is the speed of the wave in m/s?
What is the wavelength in nm?
What is the frequency of the x ray?
n = 1.37
x 10-2 /s or 1.37 x 10-2 Hz
speed = wavelength x
frequency
speed = 3.0003 x 108
m/s
l =
404 nm
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