Experiment 1 Title: - Study the characteristics of LED, the relationship between LED voltage and the wavelength of Light Emitted Objective: Study the characteristics of LED Find the wavelength of Light Emitted Apparatus: LED (Red, Green, Yellow) Power Supply (10V Variable) Resisters (1kΩ, 2.2kΩ,5kΩ,20kΩ) Theory: Like a common diode, the LED (Light Emitting Diode) consists of a P-N contact. When a PN Junction is forward biased, current flows within it. This current flow will cause electrons and holes to move is a manner that an electron will move to fill a hole. When this happens, the electron will fall to a lower energy level and this will release an amount of energy in the form of photons. In a larger scale, those photons will produce light. LEDs are diodes and to light an LED, it must be forward connected. This means that the anode of the LED must be connected to the positive pole of a battery, and the cathode must be connected to the negative pole. This is how to determine the anode and the cathode lead of an LED. Determining the anode and the cathode of a new LED is not very hard. The first way is from the length of its leads. The anode lead is longer than the cathode lead of the led. The energy radiated is proportional to the energy gap. The higher the energy gap, the greater the frequency of emitted light. Figure 1-1 Light Emitting Diode Precautions:The following careful handling tips can definitely save you a lot of time and trouble while operating with this useful equipment. The outer body of your breadboard is made up of plastic, so avoid exposing it to extreme heat. While bread boarding a circuit, the component distributions may not be that critical, but their positioning will definitely require serious attention. Avoid cramming the components and jumpers into particular compact areas; use the whole breadboard space uniformly so that tweaking and troubleshooting the circuit becomes easier. If your circuit design is critical involving highly sensitive parameters, then using a breadboard assembly probably won’t be a good idea, because the close proximity of their tracks and the jumpers may induce stray capacitance producing spurious results. Do not apply mains voltages directly to the breadboard circuitry because again the closely situated connections may possibly create arcing or even dangerous short circuits and a fire. Band Gap 𝐸𝑔 = ℎ𝑓 Since 𝐸𝑔 = ℎ𝑐/λ λ = Wavelength c = velocity of light = 3x108 m/s h = Plank’s Constant = 6.636x10-34 J.sec Vknee = Vth = Eg = VLED λ = wavelength = 1.24 / Eg Circuit Diagram: Observation (in Forward Bias) VCC R(Ω) VR VLED =EG LEDCOLOUR OBSERVATION VCC R(Ω) VR VLED=EG LEDCOLOUR OBSERVATION VCC R(Ω) VR VLED=EG LEDCOLOUR OBSERVATION Graphs Conclusion __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ Rubrics Psychomotor Domain Criteria Poor Average Good Very Good Excellent 1 2 3 4 5 More than 15 minutes late More than 10 minutes but less than 15 minutes late More than 5 but less than 10 minutes late Less than 5 minutes late Right on time Demonstrate either no, incomplete or incorrect operational skills and is unable to identity parameters and uncertainties Has basic idea but in need of extreme supervision and steering in right direction Establishes above average apparatus operational skills to utilize the apparatus effectively, with no amount of damages to the apparatus Establishes good apparatus operational skills to utilize the apparatus effectively, with no amount of damages to the apparatus Establishes excellent apparatus operational skills to utilize the apparatus effectively, with no amount of damages to the apparatus Software Usage Demonstrate either no, incomplete or incorrect operational skills and is unable to identity parameters and uncertainties Has basic idea but in need of extreme supervision and steering in right direction Establishes above average connections, operational skills to utilize the software effectively but requires supervision Establishes good connections, operational skills to utilize the software effectively with minimum supervision Establishes excellent connections, operational skills to utilize the software effectively with no no supervision Timely Completion Could not perform the experiment at all Partially completed with little meaning-fullness Completed with little extra time Completed the task within the specified period Completed the task before specified period Data Acquisition Data is incorrect or missing entirely. Relevant units or labels are missing Data is incomplete or does not include sufficient details. Relevant units or labels are incorrect Data is complete but does not comprehensive details. Relevant units or labels are partially correct Data is complete and correct. Sufficient details are provided Data is complete and correct. Student provided details. Data Analysis and Interpretation Did not analyze any data Analyzed some data but did not answer any questions Analyzed some data and answered some questions Analyzed most of the data and answered most of the questions Analyzed all of the data and answered all the questions Punctuality Equipment Usage Score Psychomotor Total Affective Domain Criteria Poor Average Good Very Good Excellent 1 2 3 4 5 Responsiveness to queries / questions Could not comprehend questions at all the Needed extra tips to comprehend the questions Took more than average time to comprehend the questions Took average or less than average time to comprehend the questions Immediately comprehended the questions Lab Work (manual) presentation No or very little write up. Missing almost all the parts in the manual. Directed to rewrite Write up of all the parts but with major mistakes. Directed to correct the mistakes Write up of all the parts but with minor mistakes. Directed to correct the mistakes Write up of all the parts with no mistakes. Few cleanliness issues in write up. No corrections required Write up of all the parts with no mistakes. No cleanliness issues in write up. No corrections required Affective Total Signature_______________ Score