Lab 3 Wave Interference (02)

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Apr 3, 2024

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LAB 3: WAVE INTERFERENCE Part A Theory Please study the Interference concept to answer the following questions. 1. Discuss interference, constructive and destructive interference. List the phase and path difference equations for constructive and destructive conditions. 2. Discuss the Double Slits (Young’s) interference. Give path difference equation for the angle condition of interference in Young’s interference. Define the meaning of each term in your equation. 3. Double slits interference shown in graph: slits separation d = 1900 nm, distance between slits and screen D = 4436 nm, central bright y o = 0, first bright position on screen y 1 = 1555 nm. Determine angle θ and wavelength λ using the given information.
4. Discuss the phase change condition due to reflection of light from a surface. Summarize equations of interference for thin films. Part B Lab Go to PhET website. Click on Simulation/Physics. Under Physics, choose Light & Radiation. Under Light & Radiation, Wave Interference is the 2nd of last simulation (Location might change. Sort with A-to-Z search.). Click to run the Wave Interference . Test and understand all functional tools on screen. You must practice figuring out what is the best way to complete the measurement. Data Table 1: Slits Simulation. Measure Wavelength λ of Light Source. Basic Operation Procedures Using Wave Interference/Slits Simulation: 1. Go to PhET website. Click on Simulation/Physics. Under Physics, choose Light & Radiation to locate the Wave Interference simulation (sort by A-to-Z search.). Click to run Wave Interference/Slits . 2. Keep the default Amplitude (Max). Press the Light icon as source (the 3 rd icon, just below Amplitude). Place check mark on Screen and Intensity. Choose Two Slits. Keep the default Slit Width a = 500 nm. Adjust Slits Separation d = 1900 nm, as shown in Sample Figure 1. 3. Slide the Frequency slider to Red (sample data). Press the Green Button on the left side screen to emit Light. Drag Slits slider ◄► on bottom of Slits to the far left. 4. Drag Ruler out of Toolbox to measure the distance, D, between Slits and Screen (as shown on Sample Figure 1). Record D value above Data Table 1. 5. Move Ruler to Screen and measure the center-to- center distance Δy between two neighbor brights (as shown in Sample Figure 1). Record Δy in Table 1 (sample data 1586.9nm). 6. Calculate/record angle θ by θ=tan -1 (Δy/D) (sample θ = tan -1 (Δy/D) = tan -1 (1586.9nm/4437.8nm) =16.67 o ), wavelength λ by λ =dsinθ (nm) (sample λ =1900nmsin16.67 o = 639.7 nm). 7. Drag Scope (top right) out of toolbox and Place both Probes (overlap them to see one single wave on scope) on wave. Press ( ) (or ►) to freeze wave patten. Measure/record period T (sample 2.2 fs) from Scope based on the time scale of Scope, as shown in Sample Figures 1.
8. Calculate the speed of light by c = λ /T (m/s) (sample data c = 639.7nm / (2.2 fs) = (639.7x10 −9 ) /(2.2x10 −15 ) = 2.9x10 8 m/s). Note: 1 nm = 10 −9 m, 1fs = 10 −15 s. 9. Repeat steps 3 to 8 for setting Frequency Slider on Yellow, Green, and Violet, respectively. Record your data in Data Table 1. Attach screenshots of each Simulation data to lab report. Data Table 1: Slits Simulation. Measure Wavelength λ of Light Source. Slit Width a = 500 nm and Adjust Slits Separation d = 1900 nm. Measured the distance, D, between Slits and Screen: D = (nm) Attach screenshots of each Simulation data to Lab Report . Color Δy (nm) θ=tan -1 (Δy/D) λ =dsinθ (nm) 1 nm = 10 −9 m T (fs) 1fs = 10 −15 s c = λ /T (m/s) Red 1586.9 19.67 0 639.7 2.2 2.9x10 8 m/s Yellow Green Violet
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Questions: If you decrease the Slits Separation d, what do you observe? If you decrease the distance between Slits and Screen D, what do you observe? Data Table 2: Interference Simulation. Measure Wavelength λ of Light Source. Basic Operation Procedures Using Wave Interference/Interference Simulation: 1. Go to PhET website. Click on Simulation/Physics. Under Physics, choose Light & Radiation to locate the Wave Interference simulation (sort by A-to-Z search.). Click to run Wave Interference/Interference . 2. Keep the default Amplitude (Max). Press the Light icon as source (the 3 rd icon, just below Separation). Place check mark on Screen and Intensity. Adjust Separation d = 2000 nm, as shown in Sample Figure 2. 3. Slide the Frequency slider to Red (sample data). Press the Green Button on the Light Sources (left side screen) to emit Light. 4. Drag Ruler out of Toolbox to measure the distance, D, between Light Source and Screen (as shown on Sample Figure 2). Record D value above Data Table 2. 5. Move Ruler to Screen and measure the center-to- center distance Δy between two neighbor brights (as shown in Sample Figure 2). Record Δy in Table 2 (sample data 1700.2 nm). 6. Calculate/record angle θ by θ=tan -1 (Δy/D) (sample θ = tan -1 (Δy/D) = tan -1 (1700.2nm/4998.5nm) =18.79 o ), wavelength λ by λ =dsinθ (nm) (sample λ =2000nmsin18.79 o = 644.0 nm). 7. Drag Scope (top right) out of toolbox and Place both Probes (overlap them to see one single wave on scope) on wave. Press ( ) (or ►) to freeze wave patten. Measure/record period T (sample 2.2 fs) from Scope based on the time scale of Scope, as shown in Sample Figures 1. 8. Calculate the speed of light by c = λ /T (m/s) (sample data c = 644.0nm / (2.2 fs) = (644.0x10 −9 ) /(2.2x10 −15 ) = 2.9x10 8 m/s). Note: 1 nm = 10 −9 m, 1fs = 10 −15 s. 9. Repeat steps 3 to 8 for setting Frequency Slider on Yellow, Green, and Blue, respectively. Record your data in Data Table 2. Attach screenshots of each Simulation data to lab report.
Data Table 2: Interference Simulation. Measure Wavelength λ of Light Source. Adjust Separation d = 2000 nm. Measured the distance, D, between Laser and Screen: D = (nm) Attach screenshots of each Simulation data to Lab Report . Color Δy (nm) θ=tan -1 ( Δy/D) λ =dsinθ (nm) 1 nm = 10 −9 m T (fs) 1fs = 10 −15 s c = λ /T (m/s) Red 1700.2 18.79 0 644.0 2.2 2.9x10 8 m/s Yellow Green Blue Questions: Calculate the average measured speed of light, as c av . Then, calculate the percent error between c av and given speed of light c = 3.0 x10 8 m/s: % error = { (given – measured) Values / [Given Value]}•100%
If you increase the Separation d, what do you observe? (Try on Simulation.) Part C Discovery Beyond what you have done with Wave Interference Simulation, make a few new findings using other functions in this simulation , or give real life examples for interference. You can express your findings by data table, word, equations, and/or screenshot graph/Video, but do give physics explanation. You could also design meaningful experiments and show them here. In Part C a minimum of 10 sentences are required.
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