(Get Answer) – Question 7: place a b filter in the beam path with the 40% neutral

(Get Answer) – Question 7: place a b filter in the beam path with the 40% neutralName:Blackbody Curves & UBV Filters – Student GuideBackground MaterialThoroughly review the “Spectra” and “Filters” background pages. The color index page may alsobe helpful to review.Filters Simulator OverviewThe filters simulator allows one to observe light from various sources passing through multiplefilters and the resulting light that passes through to some detector. An “optical bench” shows thesource, slots for filters, and the detected light. The wavelengths of light involved range from 380nm to 825 nm which more than encompass the range of wavelengths detected by the human eye.The upper half of the simulator graphically displays the source-filter-detector process. A graph ofintensity versus wavelength for the source is shown in the leftmost graph. The middle graphdisplays the combined filter transmittance – the percentage of light the filters allow to pass foreach wavelength. The rightmost graph displays a graph of intensity versus wavelength for thelight that actually gets through the filter and could travel on to some detector such as your eye ora CCD. Color swatches at the far left and right demonstrate the effective color of the source anddetector profile respectively.The lower portion of the simulator contains tools for controlling both the light source and thefilter transmittance.•In the source panel perform the following actions to gain familiarity.o Create an blackbody source distribution – the spectrum produced by a light bulbwhich is a continuous spectrum. Practice using the temperature and peak heightcontrols to control the source spectrum.o Create a bell-shaped spectrum. This distribution is symmetric about a peakwavelength. Practice using the peak wavelength, spread, and peak heightcontrols to vary the source spectrum.o Practice creating piecewise linear sources. In this mode the user has completecontrol over the shape of the spectrum as control points can be dragged to anyvalue of intensity. Additional control points are created whenever a piecewise segment isclicked at that location. Control points may be deleted by holding down the Delete key andclicking them. Control points can be dragged to any location as long as they don’t passthe wavelength value of another control point.NAAP – Blackbody Curves & UBV Filters 1/7•In the filters panel perform the following actions to gain familiarity.o Review the shapes of the preset filters (the B,V, and R filters) in the filters list.Clicking on them selects them and displays them in the graph in the filters panel.o Click the add button below the filters list. Rename the filter from the default (“filter 4”). Shape the piecewise linear function to something other than a flat line.o Click the add button below the filters list. Select bell-shaped from the distribution type pull down menu. Alter the features of the default and rename the filter.o If desired, click the remove button below the filters list. This removes theactively selected filter (can’t remove the preset B,V, and R filters). Filters are notsaved anywhere. Refreshing the flash file deletes the filters.Filters Simulator Questions• Use the piecewise linear mode of the source panel to create a “flat white light” source atmaximum intensity. This source will have all wavelengths with equal intensity.• Drag the V filter to a slot in the beam path (i.e. place them in the filter rack).• Try the B and the R filter one at a time as well. Dragging a filter anywhere away from thefilter rack will remove it from the beam path.Question 1: Sketch the graphs for the flat white light and V filter in the boxes below. What is theeffective color of the detected distribution?source distributioncombined filter transmittancedetected distributionQuestion 2: With the flat white light source, what is the relationship between the filtertransmittance and the detected distribution?NAAP – Blackbody Curves & UBV Filters 2/7• Add a new piecewise linear filter.• Adjust the filter so that only large amounts of green light pass. This will require thataddition of points.Question 3: Use this green filter with the flat white light source and sketch the graphs below.source distributioncombined filter transmittancedetected distributionQuestion 4: Use the blackbody option in the source panel to create a blackbody spectrum thatmimics white light. What is the temperature of this blackbody you created?• Add a new piecewise linear filter to the filter list.• Modify the new filter to create a 40% “neutral density filter”. That is, create a filter whichallows approximately 40% of the light to pass through at all wavelengths.• Set up the simulator so that light from the “blackbody white light” source passes throughthis filter.Question 5: Sketch the graphs created above in the boxes below. (This situation crudelyapproximates what sunglasses do on a bright summer day.)source distributioncombined filter transmittancedetected distributionQuestion 6: Remove all filters in the filters rack. Place a B filter in the beam path with the flatwhite light source. Then add a second B filter and then a third. Describe and explain whathappens when you add more than one of a specific filter.NAAP – Blackbody Curves & UBV Filters 3/7Question 7: Place a B filter in the beam path with the 40% neutral density filter. Then add a Vfilter into the beam path. Describe and explain what happens when you add more than one filterto the filter rack.purple filterQuestion 8: Create a piecewise linear filter that when used with the flatwhite light source would allow red and blue wavelengths to pass andthus effectively allowing purple light to pass. Draw the filter in the boxto the right.• Remove all filters from the filters rack.• Create a very narrow bell-shaped source distribution that is peaked at green wavelengths(somewhere close to 550 nm). Notice the color.• Expand the spread of the source distribution to maximum. Notice how the color changes.• Change the distribution source to an blackbody source peaked at green wavelengths (atemperature close to 5270 K). Again notice the color.Question 9: Using observations from the above actions, explain why we don’t observe “greenstars” in nature, though there are indeed stars which emit more green light than otherwavelengths.NAAP – Blackbody Curves & UBV Filters 4/7Blackbody – Curves Mode FamiliarizationThe Blackbody Curve Simulator has two main modes – the curves mode and the filters mode.The curves mode allows the exploration of blackbody curves including their peak wavelengthand the area under the curve which is related to their total energy production.•Learn how to add and remove curves and change their temperatures.o Click the add curve button one or more times.o Change the temperature slider. Notice which curve changes.o Select a second curve and change temperature.o Remove all but 1 or 2 extra curves.•Learn the vertical scale options. Have 2 or 3 curves in the explorer.o Change temperature with the auto scale all curves mode.o Change temperature with the auto scale to selected curve mode.o Change temperature with the lock scales mode.•Learn the horizontal scale options. Select the horizontal scale tab.o Note how changing the rightmost limit changes the view.•Use, if desired, the indicate peak wavelength and highlight area under curve options.Blackbody Curves – QuestionsQuestion 10: Create a blackbody curve of temperature 6000K and draw the shape in the box to the right. Does it have apeak? Is it symmetric about this peak?Question 11: Create a second curve using the add curve button and use the temperature slider tovary its temperature. Can you find a blackbody curve of another temperature that intersects the6000 K curve? Do you believe this would be true for two curves of any temperature?NAAP – Blackbody Curves & UBV Filters 5/7Question 12: Make sure that there is only one curve and check indicate peak wavelength. Varythe temperature of the curve and note how the peak wavelength changes. Formulate a generalstatement relating the peak wavelength to temperature. Then compare this statement with Wien’sLaw discussed in the background pages.Question 13: Select the highlight area under curve option and lock the vertical scale. Vary thetemperature of the curve and note how the area under the curve changes. Formulate a generalstatement relating the area under curve to temperature.Question 14: (Calculator Required) Complete the following table below. The “Area Ratio” is thearea for the curve divided by the area for the curve in the row above. This will tell you manytimes greater the new ratio is compared to the previous one.Curve TemperatureArea Under Curve (W/m 2 )Area Ratio3000 K6000 K12000 K24000 KCan you specify a more precise statement relating the area under curve to temperature. Is thisconsistent with what was referred to as the Stefan-Boltzmann Law in the background pages?NAAP – Blackbody Curves & UBV Filters 6/7Blackbody Explorer – Filters ModeThe second mode is the filters mode and explores the use of UBVR filters with blackbodycurves.•Unselect highlight area under curve and indicate peak wavelength. Select the filterstab.The light from a blackbody curve that passes through the UBVR filters are shown as coloredareas under the curve. It is this area which is later translated into a number for color magnitude.Remember that a magnitude is a logarithmic version of the flux (i.e. the amount of light) thatpasses through a filter and that lower numbers reflect larger fluxes. Note that this area dependson both the source and the filter. What is listed as a V value is the apparent magnitude of a star(assumed to blackbody which isn’t exactly true) through the V filter.Question 15: Vary the temperature and in the table to the rightnote the temperature in at which each filter peaks. Where are CurveUthe filters most sensitive, i.e. which temperature will give the Bstrongest response in a detector? VPeak TemperatureRQuestion 16: Use the color index feature to create a B-V index. This will compare the apparentmagnitude of a star through the B filter to that through the V filter. Plot temperature on thevertical axis and B-V on the horizontal.Temperature3000 KB-V4000 K5000 K6000 K8000 K10,000 K15,000 K20,000 K25,000 KQuestion 17: Use your graph to estimate the B-V value of a 12,000 K blackbody.NAAP – Blackbody Curves & UBV Filters 7/7 

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