A Physlet (applet) that displays Planck's blackbody radiation curve (Energy Density) vs.wavelength. The user can effectively alter the display by dragging the peak to various wavelengths. The corresponding temperature is displayed using Wien's Law. The plot also displays visible colors for each wavelength beneath the curve. A composite color is displayed to the left of the plot.
The user will gain both qualitative and quantitative understanding of Planck's radiation formula. Several properties of this curve can be investigated as the user changes temperature.
Target Student Population:
Upper and lower level undergraduate.
Prerequisite Knowledge or Skills:
Introductory physics and Modern physics, Blackbody radiation basics.
Type of Material:
Lecture/Demo, Tutorial with additional material.
As a physlet, the instructor may want to set this item up on their own server. There are some difficulties with scripted Physlets and Macintosh Computers.
Evaluation and Observation
This is a clear display of Planck's blackbody radiation formula "Energy density vs. Wavelength". The temperature can be selected in three ways: click and drag on the peak wavelength, select preset temperatures, or enter a temperature in a form field box. This interactive physlet shows the energy density of visible colors radiated at the selected temperature.
Use of the displayed units should be backed up by some discussion of Planck's formula for the energy density (the formula being plotted does not appear). There can be confusion about the meaning of "energy density" when plotted vs. frequency or vs. wavelength. The wavelength range is restricted from zero to one micron.
Potential Effectiveness as a Teaching Tool
The ability to vary the curve parameters (Temperature and or Peak wavelength) are integral to understanding blackbody radiation.
This applet shows the blackbody radiation curve quantitatively, and also shows the visible colors available.
The instructor will need to develop activities for students to use this item. There is no display of the energy density formula that is plotted.
Ease of Use for Both Students and Faculty
The item is quite simple and easy to understand.
Being able to change temperature by pointing at a peak wavelength is a nice feature. Users can change the temperature in three different ways.
If users change the tempererature elsewhere, the temperature box at the bottom of the page does not reflect the temperature being displayed.
Comments from Author:
We did not provide too much in the way of the Physics of the blackbody curve since the intent is for people to write their own html pages. The Physlet page is designed to show the capabilities of the applet and to provide example script.