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## Homework: Light

 Speed Formula c = λf Planck’s Formula E = hf Speed of Light (c) 3.00 × 108 m/s Planck’s Constant (h) 6.626 × 10-34 J· s 1 electron volt (eV) = 1.602 × 10-19 J 1 m = 1 × 109 nm 1 m = 1 × 106 µm

Show work for all calculations!

1. What is light?
2. What defines light as a wave? Hint: Define the words wavelength, amplitude, and frequency and draw a diagram to illustrate your answer.
3. What defines light as a particle (called a photon)? Hint: Discuss the meaning of the energy calculated based on the frequency of light.
4. Is the relationship between frequency and wavelength an inverse proportion or a direct proportion? Explain. (a) Sketch a graph and (b) write an equation to illustrate your answer, placing wavelength on the x-axis.
5. Is the relationship between the frequency of a photon and the energy of that photon an inverse proportion or a direct proportion? Explain. (a) Sketch a graph and (b) write an equation to illustrate your answer, placing frequency on the x-axis.
6. Define ground state in reference to the interaction between atoms and light.
7. Define excited state in reference to the interaction between atoms and light.

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1. The difference between the ground state and the first excited state for a certain element is 10.205 eV.
1. Can a photon with an energy of 5.0 eV cause the electron in the ground state to move to the first excited state? Why or why not? What happens instead?
2. Can a photon with an energy of 13.0 eV cause the electron to move to the first excited state? Why or why not? What happens instead?
3. What energy of a photon is required to cause an electron in the ground state to move to the first excited state? Why?
2. What is the frequency of the photon with an energy equal to your answer for 8 c?
3. What is the wavelength of that photon in meters? What part of the spectrum does this light belong to?
4. Find the frequency in Hz of the following wavelengths of light. Also, what part of the spectrum does each belong to?
```6.0 × 10-10 m                                             1.2 µm
```
5. Find the wavelength in m of the following frequencies of light. Convert your answer for the second frequency to nanometers. Also, what part of the spectrum does each belong to?
```5.0 × 106 Hz                                             1.5 × 1015 Hz
```
6. Find the frequency in Hz and wavelengths for the following photons with the energy shown. Also, what part of the spectrum does each belong to?
```0.472 eV                                                 2.14 × 10-18 J
```

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1. Draw a picture showing emission of light due to a transition between energy levels 5 and 2 using the energy-level diagram shown at left. Draw and label the electron and the photon in your picture.
1. Draw a picture showing absorption of light that causes and transition between energy levels 5 and 2 using the energy-level diagram shown at left. Draw and label the electron and the photon in your picture.
1. The wavelength of the red light from a traffic signal is centered at 675 nm (1 nm = 1 × 10-9 m). What is the frequency of this radiation?
2. The average distance between Saturn and Earth is about 1.4 × 1012 meters. How long does it take data (in hours and minutes) from the Cassini space probe to be transmitted from its orbit around Saturn to receivers on Earth?
3. The transition of an electron from the 4th shell of a hydrogen atom to the 2nd shell results in the emission of a photon with an energy of 4.09 × 10-19 J. What is the wavelength of this radiation? What region of the spectrum does it belong to?
4. The absorption of a photon with an energy of 2.09 × 10-18 J by an electron in the 1st shell of a hydrogen atom results in its transition to the 5th shell. What is the wavelength of this radiation? What region of the spectrum does it belong to?
This homework belongs with the Light and the Electromagnetic Spectrum Group Activity.
Last updated: Dec 03, 2013       Home