A pulsed ruby laser emits light at 694.3 nm. Consider a 18.5 ps pulse containing
ID: 1293321 • Letter: A
Question
A pulsed ruby laser emits light at 694.3 nm. Consider a 18.5 ps pulse containing 2.70 J of energy.
the physical length of the pulse as it travels through space= 5.5 mm
The number of photons in the pulse= 9.42e18
Assuming that the beam has a circular cross-section of 0.600 cm diameter, the density of photons=6.06e16
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QUESTION:
Use the exact values you enter in previous answer(s) to make later calculation(s). The ionization energy of a hydrogen atom is 13.6 eV. When a hydrogen atom absorbs a photon with this energy, the electron is ejected from the atom.
1) (a) What are the frequency and wavelength of a photon with this energy?
(b) When a photon has an energy greater than 13.6 eV, the "extra" energy (the energy in excess of 13.6 eV) goes into kinetic energy of the ejected electron. If a hydrogen atom absorbs a photon with an energy of 15.7 eV, what are the kinetic energy and speed of the ejected electron?
(c) When the light intensity is very high, it is possible for a hydrogen atom to absorb two photons simultaneously. If a hydrogen atom absorbs two photons of equal energy and the atom is just barely ionized, what are the frequency and wavelength of these photons?
Explanation / Answer
C*t = 3e8 * 14*e-12 = .0042 m
2. energy in a photon = h*f
h = planck's constant = 6.63 e-34
f = frequency = c/wavelength = 4.32e14
energy in a photon = 2.9e-19
energy/energy per photon = # of photons = 1.05e19 photons.
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