THINK AHEAD Online Lab: Wien's law Name: Date: Objective 0 Describe what happens to the blackbody spectrum as you increase or decrease the temperature. I Find the relationship between the temperature and the wavelength at the peak of the curve. Theory A black body radiator is a perfect emitter and absorber ofall possible wavelengths of radiation. Radiation curves are graphs of intensity against wavelength of radiation emitted by objects at different temperatures. Below is an example ofa radiation curve for a black body radiator. Wien's displacement law states that the peak (Itmax)of emitted inversely proportional to the absolute temperature (T) of the object. The peak wavelength (11mm) is wavelength radiation is the wavelength of light released at maximum intensity. Am x T = 2.898 x 10*3 mK BE+11 6E+11 4E+11 2E+11 Where the unit mK is metres-Kelvin, not milliKelvin. Online Experiment Setup Instructions Today's Online Lab we are going to use one of the PhET simulations. Go to the following website: 5500K 5000K 4500K 2000 m+ensihj / ram 7- visible woo Zone 3000 light %m THINK AHEAD https://phet.colorado.edu/sims/html/blackbody-spectrum/latest/blackbody- spectrum en.htm ZOOM on both Blackbody Temperature OBSERVE the Q Q Graph Values axes to adjust G R Labels 6269 K intensity value 140 Ultraviolet, Vis scaling Intensity and the shaded 8.76 x 107 Wim Sirius A - area under the 'm?/um curve SEE how the 6269 K 7141 K un CHANGE the color of the star .... 7728 K ectral Radiance (MV temperature changes with the Light Bulb temperature SAVE curves and COMPARE the DRAG to explore 0.462 spectrum at different values in Wavelength (um) 1 um = 1000 nm O different the spectrum lackbody Spectrum PHET : |temperatures Part A: Blackbody Spectrum Objects at different temperatures have their own characteristic spectrum-emission curve.@ THINK AHEAD 1. Select a temperature and write down the colour seen on the star. What type of relationship is there between a star colour and its temperature? 2. How does the temperature of a star relate to the intensity of radiation? How is this seen on the graph? 3. Why does a Sirius A looks blue if it emits light of all wavelengths? Use the graph to support your answer. 4. Why does a light bulb looks red if it emits light of all wavelengths? Use the graph to support your answer. 5. Why does a star colour at the temperature of the Sun looks white? Wien\"s law states a relationship between the temperature of a blackbody and its peak wavelength emission. @ THINK AHEAD Check the box graph values. On the table below record the values of the peak wavelength emission and its correspondent temperature. Be aware that in this case the temperature will be the independent variable, so be sure to take readings with the same interval distance. Leave the third column blank. Temperature (K) Wavelength (um) Table and peak- wavelength THINK AHEAD Plot a graph of peakwavelength (yaxis) against temperature (xaxis) on the grid. Remember to label the axis and use appropriate units. Graph 1.11 vs T What type of relationship do you recognise? Circle your answer Linear Direct Inverse Quadratic Other K M L, U, THINK AHEAD Since you have spotted the type of relationship, use the third column of the table to find the constant of proportionality. Write the mean value and its units