Engineering Physics Laboratory Manual 2024-2025 PDF

ATRIA INSTITUTE OF TECHNOLOGY Approved by AICTE, Affiliated to VTU, Belagavi Accredited by NAAC A++ & NBA DEPARTMENT OF BASIC SCIENCE ENGINEERING & HUMANITIES ENGINEERING PHYSICS LABORATORY MANUAL 2024 2024-2025 Ph...

ATRIA INSTITUTE OF TECHNOLOGY Approved by AICTE, Affiliated to VTU, Belagavi Accredited by NAAC A++ & NBA DEPARTMENT OF BASIC SCIENCE ENGINEERING & HUMANITIES ENGINEERING PHYSICS LABORATORY MANUAL 2024 2024-2025 Physics for Computer Science and Engineering Stream (BPHYS102) STUDENT NAME USN BRANCH SECTION 1  PHYSICS FACULTY SL.No. Name E mail ID initials 1 Prof. Kanchana S K [email protected] SKK (Lab In-charge) 2 Prof. Chethan P B [email protected] CPB 3 Dr. Shivaraj Watage [email protected] SW 4 Prof. Nagaveni M D [email protected] NMD 5 Prof. Shashi kumar S K [email protected] SSK 6 Prof.Vanitha N [email protected] VN PHYSICS LAB INSTRUCTORS SL.No. Name E mail ID initials 1 Mrs. Nethra K P [email protected] NKP 2 Mr. Nagendra Chari K N [email protected] NC 2  Safety guidelines for Engineering Physics Laboratory A laboratory class generally associated with risks compared to that of conventional theory classes so safety of every individual is very important. Thus, the following guidelines are designed to protect students from injuries and hazards.  Food items and drinks are not permitted inside the lab.  Confine to lose clothing and tie up long hair while performing the experiments.  A dangling jewellery may be entangled in equipment and can conduct electricity, so avoid jewellery for your safety.  Do not set any experiment setup close to the edge of the table.  Do not activate any circuit or apparatus until the teacher or instructor inspects it.  Never touch any live circuits or electrical equipment with wet hands.  Performing unauthorized experiments and the use of any equipment in an unsafe manner are strictly prohibited.  “Never look directly in the beam of a laser and light from a lamp used in an experiment”.  Do not short the electrical leads on any apparatus.  Do not take apart any apparatus or piece of instrument.  Return all equipment, components, connecting wires and devices to the lab instructor after completing the experiment.  All accidents and emergencies must be immediately reported to the laboratory instructor.  Be aware of fire extinguisher and first aid box locations in the lab. 3  DO’S & DONT’S 1. Attend LAB regularly and punctually. 2. Prepare for the practical classes before coming to LAB sessions. 3. Bring manual and record to the LAB regularly and follow instructions to carry out experiments. 4. Wear the college ID card at all times. 5. Every individual student must bring their own observation book and essential stationeries like scientific calculator, graph sheets etc. 6. Get your completed record and observation book signed before leaving the LAB for the day. 7. Mobile phones are strictly prohibited. 8. Get the teacher to verify the circuit connection before switching power supply ‘ON’. 9. Leave your lab station neat and organized manner at the end of each lab session. 10. Maintain discipline and silence. 4  COURSE OUTCOMES Subject: Physics for Computer Science and Engineering Stream Practice working in groups to conduct CO5 experiments in physics and perform precise and honest measurements 5  SYLLABUS Expt. No. Title of the experiment Expt.1 Determine the wavelength of the Laser light using diffraction grating CO5 Study of series and parallel LCR resonance and hence calculate Expt.2 CO5 Inductance, bandwidth and quality factor. Expt.3 Determine the Fermi energy of metal (copper). CO5 Expt.4 Determine acceptance angle and numerical aperture of an optical fibre. CO5 To determine the dielectric constant by charging and discharging the CO5 Expt.5 Capacitor. Expt.6 I-V Characteristics of Photodiode. CO5 Expt.7 Transistor characteristics. CO5 Expt.8 Planck’s constant using LED. CO5 Expt.9 CO5 6  Continuous Evaluation Rubrics Experiment Graph, Total Write Conduction setup/Circuit Calculations Viva voice up Procedure & Readings Marks connections and Results (7M) (8M) (5M) (15M) (50M) (5M) (10M) Average marks obtained for observation and record book (10M) Write up test (5M) LAB internal assessment marks obtained (5M) Total lab component marks (20M) 7  CONTENTS Sl. No. Name of the Experiment Page No. 1 LASER DIFFRACTION 9-11 2 SERIES AND PARALLEL RESONANCE 12-15 3 FERMI –ENERGY 16-17 4 OPTICAL FIBRE -NUMERICAL APERTURE 18-19 5 DIELECTRIC CONSTANT 20-22 6 PHOTODIODE CHARACTERISTICS 23-24 7 TRANSISTOR CHARACTERISTICS 25-27 8 PLANCK’S CONSTANT USING LED’S 28-29 9 8  1. LASER DIFFRACTION Aim: To determine the wavelength of the Laser light using diffraction grating. Apparatus: Diffraction grating (500 LPI), diode LASER source, image screen, meter scale. Principle: Laser is a monochromatic, coherent and intense beam of light. When laser falls on a grating, it undergoes diffraction and produces alternative bright spots on the screen. The spots become well observable if the grating constant is comparable with the wavelength of the laser. If θm is the angle through which light is diffracted to give the mth order diffraction then the condition to be satisfied is d sin θm = mλ In the experiment, grating of known value of grating constant is used. When laser is incident on it, the spots produced due to diffraction are recorded on the screen. If ‘f’ is the distance between the grating and the screen, Xm is the distance of the mth spot from the central maximum, then the angle θm can be measured using = tan−1(Xm/ ) If N is the number of lines per unit length of the grating, then the grating constant is determined by using the formula d = 1/ N Formula: Wavelength of laser source λ is given by, = Where, = tan−1(Xm/ ) m – The order of the spots λ – The wavelength of the laser light in nm d – The grating constant θm – The angle of diffraction of the mth order spot Observations: 1. Distance between the grating stand and screen, f =.....................m. 2. Grating constant or the distance between two consecutive rulings on grating For 500 LPI, d =5.08×10-5 m 9 Ray Diagram: Procedure: 1. The laser is placed on an experiment table and switched on. At about a meter away on the path of the laser a white laminated wooden screen is placed. The leveling screws of the laser are adjusted such that the laser beam exactly falls on the centre of the screen. The exact distance between the grating stand and image screen are noted, f = 100 cm = 1m. 2. The 500 LPI grating is now placed on the grating stand close to the laser source and the diffraction pattern is observed as shown in the figure. (The equally spaced diffracted laser spots are observed on either side of central maxima. The central maximum is very bright and as the order of diffraction increases the brightness decreases). 3. The centre of the spots of the diffraction pattern are marked placing a paper or graph sheet on the screen using pencil and after marking the diffraction pattern, the image screen is removed and the distances between consecutive order of diffraction is measured using a scale. 4. The distance between the two first order diffraction spots is measured as 2x1cm cm. 5. Similarly the distance between second order diffraction spots is measured and recorded as 2x2cm. This is continued up to 8th order, 2x8cm and the readings are tabulated. -1 6. Using equation θm = tan (Xm/f) diffraction angle are calculated for various orders of diffraction and are noted in tabular column. 7. Using equation, λ= (d sinθm)/m /m wavelength of given laser source is calculated for various orders of diffraction and the average wavelength is obtained. 10 Tabular Column: Diffraction Distance Diffraction angle Wavelength order ‘m’ 2Xm (cm) Xm (cm) θm = tan-1(Xm/f) = in (nm) Sin θm 1 2 3 4 5 6 7 8 λaverage = ……. nm Result: The wavelength of given laser light by diffraction method using grating is λ = …… nm 11  2. SERIES AND PARALLEL RESONANCE Aim: To study the frequency response characteristics of a series and parallel resonance circuits and hence to determine the resonance frequency, bandwidth, quality factor of the circuits and the unknown inductance of an inductor. Apparatus: Audio frequency generator, Decade inductance box, Decade capacitance box, resistance box, ammeter, connecting wires. Principle: In a series resonance circuit, the current depends on the frequency of the input voltage. With the increase in frequency, the inductive reactance (XL) increases and capacitive reactance (XC) decreases. At resonance (XL = XC) the output voltage and current are in phase and have maximum value. Knowing the capacitance and resonant frequency, inductance, band width and the Quality factor value are calculated. But in a parallel resonant circuit, at resonance with resistance in the inductance arm, the current in the increase arm is equal to the current in the capacitance arm (IL = IC) the impedance is maximum and hence the current is minimum. The output voltage and current are out of phase. By measuring the resonant frequency, the inductance of the given coil can be calculated. Formula: The unknown inductance of an inductor in the circuit is given by 1 = 2 2 Henry 4 Where, L – Unknown value of inductance in Henry C – Value of capacitance, in Farad. fr – Resonance frequency in Hertz The bandwidth is given by, Bandwidth = (f2 - f1) Hertz Where, f2 – Upper cut-off frequency in Hertz f1 – Lower cut-off frequency in Hertz. The quality factor can be calculated from the graph as, ℎ = ( 2− 1) And it can be calculated theoretically using the formula, =1 L graph R C 12 Circuit diagram: Nature of the graph: Series Resonance Parallel Resonance Procedure: 1. The electrical connections are made as shown in the circuit diagram. 2. Switch on the power supply and set the amplitude to maximum. 3. The frequency generator is switched on and increase the frequency in suitable steps from 200Hz to 3600 Hz (sine wave form) and note down the corresponding readings of the current in the ammeter. For series resonance circuit: 1. A graph is plotted by taking frequency along the X-axis and current along the Y-axis. 2. The frequency corresponding to the maximum value of current (Imax) which is called resonance frequency (fr) is noted from the graph. 3. The maximum value of current (Imax) of a resonance curve for a particular value of C is noted. 4. A straight line parallel to X - axis corresponding to the value of Imax/√2 is drawn on the curve such that the line cuts the curve at two points on either side of the resonance frequency. 5. The frequencies f1 and f2 corresponding to these points are noted from the graph and the bandwidth (f2 ~ f1) is calculated for series LCR circuit. 6. The quality factor of the circuit and the inductance of an inductor are determined by using the above relations. 13 For parallel Resonance Circuit: 1. A graph is plotted by taking frequency along the x- axis and current along the Y-axis. 2. In this case the resonance occurs when the current in the circuit is minimum. 3. Hence, the frequency corresponding to Imin gives the resonance frequency fr of the circuit. 4. A straight line parallel to X- axis corresponding to the value of (Imin×√2 ) is drawn on the curve such that the line cuts the curve at two points on both side of resonance frequency. 5. The quality factor of the circuit and the inductance of an inductor are determined by using the above relations. Tabular column: Series resonance circuit Parallel resonance circuit C = 0.1 µF, R = 750 Ω C = 0.1 µF, R = 750 Ω Frequency Current reading Frequency Current reading in Hz I in mA in Hz I in mA 200 200 400 400 600 600 800 800 1000 1000 1200 1200 1400 1400 1600 1600 1800 1800 2000 2000 2200 2200 2400 2400 2600 2600 2800 2800 3000 3000 3200 3200 3400 3400 3600 3600 14 Result: Series Resonance circuit: The series resonance frequency fr =.................................. Hz. Bandwidth =…............................. Hz. Quality factor Qgraphical = ……………….. Qcalculated = ……………….. Inductance of an inductor L =................................ Henry. Parallel Resonance Circuit: The parallel resonance frequency fr=................................. Hz. Bandwidth =…............................. Hz. Quality factor Qgraphical = ……………….. Qcalculated = ……………….. Inductance of an inductor L =................................ Henry. 15  3. FERMI ENERGY Aim: Determination of Fermi energy of given specimen (copper wire). Apparatus: Copper coil, D C regulated power supply, milli ammeter (mA), voltmeter (mV), heating arrangement , Thermometer 0-100 oC, copper wire, patch cards, etc. Principle: Metals have positive temperature coefficient of resistance. When the temperature of a metal increases its resistance also increases. By noting the change in resistance with temperature for copper metal and knowing the density of copper, its Fermi energy can be calculated using the formula. Formula: ∆ Fermi energy, = ∆ Fermi temperature, TF = E F k Where, n – The electron density of copper (8.464x1028/m³) r – The radius of copper wire (0.26x10-3 m) L – The length of the copper wire (3.6 m) – The electron mass (9.1x10-31 Kg) e – The charge of an electron (1.602x10-19C) k – The Boltzmann constant (1.38x10-23 J/K) A –Cross sectional area of copper wire (8.163x10-6m2 ) Circuit Diagram: Nature of Graph: 16 Procedure: 1. The wire is wound over an insulating material to form a coil. 2. The coil is immersed in pre-heated water as shown in the figure. 3. A thermometer is immersed in the beaker containing water and coil. 4. Temperature of the copper coil is placed in water beaker around 80oC then for every 3oC decrease in temperature note the corresponding milli-ammeter and milli-voltmeter readings are noted down in the tabular column. 5. Plot the graph of Resistance in ( ) versus Temperature in (K) and calculate the slope[∆ /∆ ] Tabular column: Sl. Temperature Resistance no. Voltage Current ( ) = in  in K in mV in mA I 0 in C (T+273) 1 2 3 4 5 6 7 Result: Fermi energy of the given copper metal is found to be EF = ………….e.V Fermi temperature of the given copper metal is found to be TF =………….K 17  4. OPTICAL FIBRE - NUMERICAL APERTURE Aim: To determine the Acceptance angle and Numerical aperture of the given optical fibre. Apparatus: Laser source, Optical fibre, Screen, Scale. Principle: The Sine of the acceptance angle of an optical fibre is known as the numerical aperture of the fibre. The acceptance angle can also be measured as the angle spread by the light signal at the emerging end of the optical fibre. Therefore, by measuring the diameter of the light spot on a screen and by knowing the distance from the fibre end to the screen, we can measure the acceptance angle and there by the numerical aperture of the fibre. Formula: The Acceptance angle,   tan1( ) Where, D – The diameter of the bright circle formed on screen. L – The distance between the optical fibre end and screen. The Numerical Aperture, NA  sin(0 ) Diagram: 18 Procedure: 1 Switch on the laser source and adjust the distance between output end of the optical fibre and the screen ‘L’ (say 2 cm). 2 Place a graph sheet on the screen and observe the circle formed on the graph sheet. 3 Mark the points ‘a, ’b, ’c’ &‘d’ on the inner bright circle as shown in the diagram. Note down the horizontal diameter D1 and vertical diameter D2 of the inner bright circle in the tabular column. 4 Repeat the above steps for different values of L (for 6cm, 8cm…….). 5 Find the Acceptance angle from the tabular column and hence the Numerical aperture. Tabular column: Trail L Horizontal Vertical Mean Acceptance Numerical No. (in cm) diameter D1 diameter D2 Diameter angle aperture (in cm) (in cm) D(in cm)   tan1( ) NAsin 0 1 6 2 8 3 10 4 12 5 14 (θ0) mean= ……in degree (NA) mean= - - - - Result: 1. The Angle of acceptance of the given optical fibre is found to be, (θ0) = …………….. 2. The Numerical aperture of the given optical fibre is found to be, NA =……………… 19  5. DIELECTRIC CONSTANT Aim: To determine dielectric constant of a material within a parallel plate capacitor by using a DC charging and discharging circuit. Apparatus: Constant 5V DC power supply, digital voltmeter, timer, resistor of known values and capacitor with known values of dimensions, circuit unit and patch cords. Formula: 1 2 = 0.693 0 Where, 0– The capacitance of the capacitor without the dielectric medium 0= ∈0A/d = 26.55µF K – The dielectric constant of the material within the capacitor T1/2 – The time in seconds required to get charged / discharged to 50% of the capacitance value R – The resistance in the circuit in (Ω) Circuit diagram: 20 Nature of graph: Procedure: 1. The circuit connections to be made as shown in diagram. 2. The supply points are switched on. 3. The 5v constant DC power supply connected to the charging (C) and discharging (D) modes. 4. The given resistor (R=100×103 ) is connected between the timer and the capacitor. 5. The given capacitor (C1) is connected between the constant DC power supply. 6. The voltmeter is connected parallel to the capacitor. 7. To begin with, the toggle in the switch S2 is set to halt position. The timer is set to zero by pressing the reset button. The digital voltmeter in the circuit reading is zero. Charging mode: 1. To start with, the toggle of the switch S1 is set to charging mode (C). 2. The toggle in switch S2 is set to start position, at which instant the capacitor begins to get charged to higher voltage and the timer starts counting simultaneously. 3. Immediately start noting down the voltage readings ‘V’ in the tabular column at every 5 seconds interval from 0 to 70 s, until V become practically constant (i.e. reaching saturation voltage). Under charging mode, the initial readings must be V= 0 for T= 0. 21 Discharging mode: 4. The toggle of the switch S2 is changed to halt position. 5. The timer is reset to read zero. 6. The toggle in switch S1 is changed to discharge mode and simultaneously set to start position. 7. Immediately start noting down the reading for V at every 5 seconds interval from 0 to 70 s until V become practically constant (minimum saturation value) i.e. constant over two consecutive observations. 8. The readings for V are tabulated under discharge mode. Under discharging mode the initial readings must be V= maximum for T= 0. To find T1/2: 1. From the tabular column readings, a graph is plotted with time T in seconds taken along X-axis and the voltage V in volts along Y-axis the charge mode curve and the discharge mode curve intersect at a point P. 2. By referring the position of Pin X-axis, the value of T1/2 in sec is found out. The value of the dielectric constant K is calculated using the formula. Observations: 0= ∈0A/d = 26.55µF T1/2 = sec The resistance, R= Ω 22 Tabular column: Time ‘T’ R = 100k in Voltage across C in volts V seconds Charge mode Discharge mode 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Result: The dielectric constant of the material in the capacitor is found as K = ……………. 23  6. PHOTODIODE CHARACTERISTICS Aim: To study the reverse bias characteristics of the photodiode and hence to find the Responsivity. Apparatus: Photodiode, Bulb, power supplies and Ammeter, micro ammeter, Voltmeters. Principle: Photodiode is a two terminal junction diode in which the reverse saturation current changes when it’s reverse biased junction is illuminated by suitable wavelength of light. This small amount of reverse saturation current is due to thermally generated electron-hole pairs. The number of these minority charge carriers depends on the intensity of light incident on the junction. When the diode is in a glass package, light can reach the junction and thus changes the reverse current. circuit diagram: µA - + + - Photo - A - diode - 0 – 5V 0 – 15 V V V Source Source + Bulb + + Model Graph: ( reverse bias characteristics of the photodiode) 24 Tabular column: For various Intensity of the LED Sl. Low intensity Moderate intensity High intensity No (11mW) (21 mW) (30mW) Biasing voltage Current Biasing Current Biasing Current in volts (I) in A voltagein (I) in A voltagein (I) in A volts volts 1 0 0 0 2 0.2 0.2 0.2 3 0.4 0.4 0.4 4 0.6 0.6 0.6 5 0.8 0.8 0.8 Procedure: - To study the reverse bias characteristics of the photodiode. 1. The electrical connections are made as shown in the circuit diagram. 2. Set the intensity of the LED to any “low intensity” value. 3. Set the voltage value to 0.2V and note down the corresponding ammeter reading on microammeter and extending voltage values till 2V. 4. The experiment is repeated by varying the intensity of the LED for 11mW(low intensity), 21 mW(moderate intensity) and 30mW(high intensity) of power values. 5. The graph is plotted between current versus voltage for different intensity of the bulb in the third quadrant of the graph, because the current and voltages are for the reverse bias. 6. The characteristics of photodiode in reverse bias condition are obtained as shown in the specimen graph. Result: - The photodiode characteristics of reverse bais are represented in the graph.. 25  7. TRANSISTOR CHARACTERISTICS Aim: To study the input and output characteristics of the given NPN transistor in the common emitter mode and calculation current gain, amplification factor& knee voltage. Apparatus: Given Transistor (NPN), variable DC power supply, DC micro ammeter, DC milli ammeter, DC voltmeter, patch cords. (All these devices are internally connected in the kit). Principle: Transistor is a three terminal semi-conducting device basically used for amplification. It is operated in three different modes viz., CE mode, CB mode and CC mode. In any transistor emitter-base junction is always forward biased and collector-base junction is reversed biased. In CE mode, the following characteristics are studied. Input characteristics: The study of variation in input current (base current) with input voltage (base−emitter voltage) at constant output voltage (collector−emitter voltage). Output characteristics: The study of variation in output current (collector current) with output voltage (collector−emitter voltage) at constant input current (base current). Formula: β1 =( ₂‒ ₁)/( ‒ ), β2=( ₃‒ ₂)/( ₃‒ ₂) and β 3= ( ₃‒ )/( ₃‒ ) IC  IB 1 β = (β1+β2+β3)/3 Where, β – The current amplification factor, IB  I B 2  I B1 , The change in the base current, I C  I C 2  I C1 , The corresponding change in collector current. α= 1+ Where, α – The current gain in common-base mode. 26  Circuit Diagram: Procedure: 1. The common emitter circuit for studying the transistor characteristics of a NPN transistor is as shown in the figure. 2. Identify the base, the collector and the emitter leads of the given NPN transistor and then insert it into the transistor socket in the circuit. 3. Before switching on the circuit, turn all power supply knobs to the minimum position. Input characteristics: 1. The DC voltmeter is connected across collector-emitter junction. 2. The collector emitter voltage VCE is set to 2 volt by varying VCE. 3. The voltmeter is disconnected and then connected across base-emitter junction. 4. Keeping VCE = 2 volt as constant, the base-emitter voltage VBE ( input voltage) is increased from zero volt in steps of 0.1 V upto 0.8 V, by varying the knob VBB and the corresponding values of base current IB are noted from the milli ammeter. 5. A graph of VBE along X-axis and IB along Y-axis is plotted. Output characteristics: 1. The DC voltmeter is connected back across collector-emitter junction. 2. The base current IB is fixed for constant value say 25μA and the collector emitter voltage VCE is increased from zero volt in steps of 0.1 V up to 1V and the corresponding values of collector current IC are noted from the milli ammeter. 3. The experiment is repeated for 50μA and 100μA, the corresponding collector current values are tabulated. 4. A graph of VCE along X-axis and IC along Y-axis is plotted. 27 Nature of graph: Tabular column: Input Characteristics Output characteristics VCE = 2V IC (mA) VBE (V) IB (µA) VCE (V) IB1 = 25 µA IB2 = 50 µA IB3 =100 µA 0 0 0.1 0.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 0.5 0.6 0.6 0.7 0.7 0.8 0.8 Result: For a given NPN transistor, 1. The knee voltage, VK =.......................... V 2. The value of β = …………………. 3. The value of α = …………………. 28  8. PLANCK’S CONSTANT USING LED’S Aim: To determine the Planck’s constant using known wavelength LED source. Apparatus: Planck’s constant experimental setup consisting of 0 – 10V peak to peak sine wave generator, digital peak reading voltmeter, five different known wavelength LED sources. Principle: Planck’s law states that Emission or absorption of radiation by a black body does not take place in continuous steps but in discrete units each such unit is called photon or quanta. Energy carried by each photon or quanta is given by hc E  h.  ----------------(1)  If V is the forward voltage applied across the LED terminal that makes it to emit light, then the energy given to the LED is given by E  e.V------ ------ (2) Comparing Equation (1) and (2), we get e.(V)mean ) h C Formula: e. (V)mean Planck’s constant, h  J.s C Where e - Charge of the electron = 1.6 x 10-19C C - Velocity of light in free space = 3 x108 m/s λ - Wavelength of the LED in meter (m) V - Forward knee voltage of the LED in volt (V) Circuit Diagram: Fig. Knee Voltage Determination 29 Procedure:- 1. The circuit is constructed as shown in the circuit diagram. The rectified output appears across the LED is a unidirectional pulsating. Hence, a peak reading meter is used to read voltage across of the LED. 2. Using a digital peak reading voltmeter, the voltage across the LED is measured and recorded in the tabular column for given color LED light. 3. Trial is repeated by changing the LED and the corresponding knee voltage is noted in the tabular column. 4. The product of wavelength and knee voltage is determined and its average value is calculated. 5. Planck’s constant is calculated using the equation, e. (V )mean h C Tabular column:- Wavelength Knee Voltage (V) Color λ V x 10-9 in λ (nm) V1 V2 Average V ( mili Volt) Orange / 563 Yellow Green 545 Blue 358 Red 630 Infrared(IR) 977 Vλmean=...................... mili Volt Result:- The Planck’s constant using known wavelength of LED source is found to be, h =………. J.s 30 31