Engineering Physics Laboratory Manual (R24) Practice Flashcards

This set of flashcards covers key vocabulary, definitions, physical constants, and experimental concepts from the Engineering Physics Laboratory manual, including semiconductor physics, optics, and electrical measurements.

Energy band gap ($E_G$)

The fundamental property of a semiconductor material determined by studying the variation of reverse saturation current ($I_D$) through a pn junction diode with absolute temperature ($T$).

Boltzmann constant ($k_B$)

A physical constant used in the diode current formula, defined in this manual as $1.38 imes 10^{-23} J/K$.

Intrinsic semiconductor

A pure semiconductor material that consists of no impurities or dopants.

Extrinsic semiconductor

A semiconductor material containing dopants, specifically acceptor type ($p$-type) with group III elements or donor type ($n$-type) with group IV elements.

Fringe width ($\beta$)

The gap between successive dark fringes formed due to interference in a wedge-shaped air film.

Normal incidence

A condition where light rays fall on a surface perpendicularly, resulting in an angle of incidence and angle of refraction of zero.

Cauchy’s Constants

Material constants $A$ and $B$ in the formula $\mu = A + \frac{B}{\lambda^2}$ which describes the refractive index of a prism material relative to wavelength.

Angle of minimum deviation ($D_m$)

The smallest angle by which light is bent by a prism for a specific wavelength, used to determine the refractive index ($\mu$).

Radius of Curvature ($R$)

The property of a convex lens determined in Newton’s Rings experiment using the formula $R = \frac{D_m^2 - D_n^2}{4\lambda(m - n)}$.

Back-lash error

An error in measurements made with a traveling microscope caused by improper calibration or play in the screw controlling the motion of the microscope.

Diffraction grating

An optical device with many parallel rulings, such as 12000 lines per inch (LPI), used to separate light into its component wavelengths.

Planck’s constant ($h$)

A fundamental constant determined by studying the cut-in voltage of Light Emitting Diodes (LEDs) using the formula $h = \frac{\lambda eV}{c}$.

Cut-in voltage ($V$)

The knee voltage at which an LED starts allowing a non-zero current (typically around $1\,mA$) to flow in the record of forward voltage characteristics.

Ordinary ray ($\mu_o$)

One of the two rays produced by double refraction in a Quartz prism that follows the standard laws of refraction.

Extraordinary ray ($\mu_e$)

One of the two rays produced by double refraction in a Quartz prism that does not follow the standard laws of refraction.

Potentiometer bridge

A resistive wire 10m long with uniform cross-section used to calibrate low range voltmeters and ammeters by finding balancing lengths.

Laser diode

A semiconductor device used as a light source to determine wavelength via diffraction grating, where $\sin(\theta) = \frac{y}{\sqrt{y^2 + 4d^2}}$.

Thermistor

A thermally sensitive resistor made from semiconducting materials such as metal oxides ($Mn_2O_3$, $NiO$) or single crystal semiconductors like Ge and Si.

Activation energy ($E_a$)

Energy related to the energy band gap of a semiconductor that determines the temperature dependency of charge carrier concentrations ($n$ or $p$).

PTC (Positive Temperature Coefficient)

A characteristic where the electrical resistance of a material increases as the temperature increases.

NTC (Negative Temperature Coefficient)

A characteristic where the electrical resistance of a material decreases as the temperature increases; typical for metal oxide thermistors.

Wheatstone’s bridge

A circuit of four resistors ($R_1, R_2, R_3, R_4$) used to determine an unknown resistance when the galvanometer shows zero deflection, satisfying $\frac{R_1}{R_2} = \frac{R_3}{R_4}$.