Light Worksheet / Bohr Model

Below are the solutions to the Light Worksheet. Be prepared to take a quiz on problems associated with this worksheet tomorrow, Tuesday, March 30th.

Material Covered on Wednesday, March 17th

Please look at the previous post for the electromagnetic spectrum chart that you need to print. The material covered today is listed below.

1. The dual nature of light. How light can have both wave and particle properties.
2. The particle nature of light has a momentum like quality. Therefore, when light particles (photons) strike a photovoltaic cell, the light can displace the electrons in the cell and cause an electric current.
3. Two demonstration were performed. The first was using a photovoltaic cell, three LED lights (orange, green, and blue) and a volt meter. Each light was projected on the photovoltaic cell and the voltage produced from the cell was measured. The correlation between voltage and energy is direct. Therefore, a larger voltage produced by a color of light means a larger energy is associated with that frequency of light. The demonstration confirmed the relationship between frequency of electromagnetic radiation and energy.
4. The second demonstration was the heating of a steel rod in a flame from a Fischer burner. The black body (steel rod) began to emit visible light after a certain amount of energy was absorbed. Once again, the visible light seen correlated to ROYGBIV with more energy absorbed resulting in a higher frequency light emitted.
5. The discussion was begun on the Bohr model of the hydrogen atom. The premise is that specific frequencies of light are emitted from a hydrogen atom when electrons are excited and then "fall" back to the ground state. The farther the "fall", the higher the frequency of light emitted.

*As a side note, Evan S. and Eric B. missed the one week that I addressed a number of their far out and obscure theoretical physics questions. Evan and Eric, see me when you get back, I have a lot to show you.

Electromagnetic Chart

Because color copies are beyond our budget, please print a copy of the image above of the electromagnetic spectrum from your home computer / printer. You will need this chart to answer questions on the Bohr model worksheet. Also, know the conversion from meters (m) to nanometer (nm). (1 x 10^9 nm = 1 m) You will need to do this conversion to determine the wavelength of visible light in nanometer. This in turn will allow you to determine what color of light is emitted or absorbed by using the electromagnetic chart.

Material Covered on Tuesday, March 16th

For those of you abscent on Tuesday, March 16th, the following was covered.

1. Wave concepts were reviewed and refined. This included the relationship between wavelength and frequency (inverse) and the product of the two values being the velocity of a wave.
2. We discussed light as a wave and demonstrations were offered to offer support that light travels as a wave, and thus follows all of the criteria of a mechanical wave (i.e. - a wave traveling through a spring).
3. The relationship between frequency of a wave and enerygy was developed. The higher the frequency of a wave, the higher the energy.

All material covered is in the notes package (Power Point presentation) given out.

Ion Separation Lab

Your write-up for the ion separation lab will be due on Friday, March 19th, 2010 (the Friday before spring break). Please follow the instructions given to you in the packet. Also, use the hand-out for typing help in Word. Everything can be typed, so you may have to learn a thing or two about Word to complete the write-up to an acceptable level. Look at the section in the typing help for how to type chemical equations. Remember, the appearance of this lab should look professional. I am open to different formats as long as the basic criteria for the format are met and it is neat, orderly, and easy to follow. Below is the rubric for how your report will be scored. E-mail me at cbruecker@lps.k12.co.us or see me if you have any questions or need any help.