Flashcards
4D
Flashcards do conjunto (23)
- 1Harmonic motion = motion that regularly repeats; *can NOT use uniform a Hooke's law: restoring force exerted by spring = minus k (spring constant) * displacement (+ve - stretched, -ve - compressed) EPE of spring = 0.5 * k * x^2 = work against springMaximum EPE (@ amplitude) = maximum KE (@ equilibrium)
Maximum speed = x_A * sqrt [k ./. m]
Frequency = v ./. [2 * pi * x_A] = sqrt [k ./. m] ./. [2 * pi]; actually independent of x_A
Gravity affects equilibrium position \ oscillation still simple harmonic - 2Simple pendulum = connecting string has negligible mass, no friction @ suspension point during oscillation; displacement = angle made with vertical, NOT distance from equilibrium, NOT proportional to restoring force unless angle small enough to regard sin negligible Frequency = sqrt [g ./. L] ./. [2 * pi].
- 3Sound = KE transferred from oscillating air to eardrum Front of speaker = diaphragm of speaker; oscillates back and forth to cause air to oscillate Center line - undisturbed position of airSpeed of sound = 343 m s^-1; does not change unless properties of medium changed
Velocity (v) = sqrt [Bulk modulus ./. density]; Bulk modulus measures rigidity (hardness to compress), usually far outweighs increase in density - 4Decibels = 10 * log_10 [intensity ./. threshold]; threshold = 10^-12 W m^2 Intensity = power ./. area; power spreads out over larger area when sound dissipates to longer distances Energy gets lost to medium (attenuation)Human hearing range: 20 Hz to 20 kHz
Ultrasound has low vavelength --> less diffraction -- clear images can be formed
Transducer converts electrical energy into sound energy (pulse) -> some reflects back to transducer when hitting another medium -- time received indicates distance - 5Standing waves = caused by interference of opposite waves of equal x_A and f Open-open tube: air @ both ends (antinodes) free to oscillate; open-closed tube: open end @ antinode \ closed end @ node (don't move) Length of tube decreases with amount of substanceFundamental wavelength = sound wave with longest wavelength (first harmonic, lowest frequency)
Multiple wavelengths can exist in tube simultaneously
Possible wavelengths for open-open tube vs open-closed tube: 2 L ./. (integer) n vs 4 L ./. (odd) n - 6Beats vs standing waves: different f vs same f, wobbling wave (beats @ equally spaced moments of constructive interference) vs harmonic, changing amplitude vs constant amplitude Beat frequency = | f_1 minus f_2 |.
- 7Doppler effect: moving sound source distorting wavelengths of sounds in front and behind -- perceived frequency distorted Observed f = source f * [v + obs v] ./. [v minus source v]; +ve v - source away from obs +/ obs towards source, -ve - source towards obs +/ obs from sourceSource and wave moving @ same velocity (source towards obs) -- source remains with wave front, sounds produce continuously add to wave front via constructive interference --> air highly pressurised, heard as sonic boom (sound energy reaches obs @ once)
- 8Shockwaves - region of constructive interference occurs as 3D cone not wall (source v > wave v); smaller angle of cone if source moves faster Triangle diagram for shockwaves: hyp - distance travelled by object, opp - distance sound wave travelled from point source.
- 9Polarised light: electric field oscillate @ single direction (linear // circular if >2 overlapping) Applications of partially polarised light: sunglasses polarise light with same oscillation as glare, 3D glasses each lens allows vertically polarised vs horizontally polarised (or CW vs CCW).
- 10Diffraction = light spreading out after getting through tiny hole Double split interference: light forced into two beams -> constructive or destructive interference @ wall -> alternating light vs dark spots; gratings reduce smudging (via pairing deviations) + increase bright spotsYoung's double slit experiment: two holes (small enough as slits) spaced apart @ similar distance as wavelength, laser wide enough to hit both -- smudgy bright spots, die off from m > 5
Difference in pathlength (dx) = order (m from 0 onwards) * wavelength ~= inter-slit distance * angle from center line - 11Huygen's principle: every point @ wave as source of another wave spreading out spherically --> infinite waves eventually interact to add up to same wave; single slit interference introduces barrier to allow only certain waves to go throughSingle slit interference equation: order (m of destructive points, from 1 onwards) * wavelength ~= slit width * angle from center line
- 12Thin film interference: light hits interface of two mediums -> some pass through \ some reflect -> interference between reflection from two mediums pi shifting = starting position shifted to opposite phase (eg crest <-> valley), occurs if hit medium of greater refractive indexRefractive index = c ./. speed of light @ medium
Thin film equation: dx = 2 * thickness = order * wavelength @ thin film
Application of thin film destructive interference = antireflective coating (layer gives pi shift \ material beneath does not) - 13Stretching vibration - oscillation of spring @ covalent bonds IR diagnostic region - particular functional group (eg v~ 2100); fingerprint region - unique to molecule including single C-C (usually < v~ 1500)Frequency of oscillations = nu = sqrt [spring constant (k) ./. reduced mass] ./. [2 * pi]
Stronger bonds have greater frequency of oscillations (because spring constant) - 14Wavenumber = 4.1162 * sqrt [k ./. amu] Single bond k = 5 * exp5 (weakened by H-bonding); double bond - 10 * exp5 (weakened by resonance); triple bond - 15 * exp5 (most s character, closest to nucleus) Dipole moment (= partial charge * distance) increases intensitysp3 C-H - usually ~2900; sp2 - ~3100; sp - ~3300; C=C - ~1650; C-=-C - ~2100
Carboxylic O-H usually wide rounded peak ~3000
N-H symmetric stretching - ~3300; asymmetric - ~3400 (more energy)
Anhydride C=O symmetric - ~1740; asymmetric - ~1800 - 15UV-Vis (200-800nm) absorption - wavelength inversely related to energy difference between LUMO and HOMO (eg pi -> pi* for bonding pi e- // n -> pi* for non-bonding lone pairs) Conjugation lengthens wavelength absorbed (otherwise absorb @ UV).
- 16MRI: B aligns with water molecules in some way (1H twists orientation to align with B field) -> radio-frequency EM wave pulses (weaker field) disrupt B field (1H misaligns transiently) -> gradual realignment -> re-release EM waves (interfered by different tissues) -> MRI records locationsIntensity / time of re-emission affected by thickness / hardness of tissue
Increasing quality of MRI: stronger stationary B / multiple imaging / contrast agent (eg Gd^3+, disrupts effective B experienced by 1H)
fMRI: e- of oxygenated blood blocks applied B field --> screens 1H - 17NMR vs MRI: generate information based on f of emitted radiation vs intensity Alpha vs beta spin: along with external B field vs against (in resonance) dE between spin states related to h * u (radio-wave range); increased if stronger applied BFT-NMR: excess of nuclei @ alpha state -> short pulse with different range of frequencies -> nuclei @ alpha state assume beta state -> fall back down to alpha state -> re-emit radio wave -> detected for each absorption frequency
- 18Diamagnetism = e- encircling 1H creates induced B field directly opposing applied B field --> 1H experiences smaller B field (shielded) Older types of NMR - frequency constant \ B field varied (upfield vs downfield -- higher vs lower strength required)Chemical shift = observed from TMS * exp6 ./. spectrometer frequency
EN atoms make C atom d+ --> pulling away shielding electrons --> 1H more de-shielded; EWG @ sp2 carbon withdraws more e- density than @ sp3
H-bonding can make 1H more de-shielded - 19Diamagnetic anisotropy: eg benzene 6 e- circulate to induce B field same direction as applied B field (applies for outer ring; \ works against if @ inner ring) --> experience greater B field Triple bonds recirculation --> induced B against applied BSpin-spin splitting (coupling): induced B field of other 1H work in same direction // opposite direction -> greater // smaller effective B -> greater // smaller chemical shift
n+1 multiplicity rule - for equivalent neighbours; complex splitting for non-equivalent neighbours - 20Thin lens conventions: magnification 1 = object size, +ve - right way up Concave vs convex lens: opens inward (diverging) vs outward (converging) Focal point = convergence of parallel rays Principal axis = pass through center of lensLens equation formula: 1./.f (+ve for converging \ -ve for diverging) = 1./.d_o + 1./.d_i (+ve for real \ -ve for virtual)
Magnification = -ve of d_i ./. d_o; multiply individual values for multiple lens - 21Lens power = 1./.f, indicates impact on light trajectory High power lens - more convex Chromatic aberration = greater frequency gets bent more; spherical aberration = away from center gets bent more (worse for more convex / spherical)Nearsighted vs farsighted: image in front (too far) vs behind retina (too near), need concave (makes object nearer) vs convex lens (makes object further)
Ciliary muscles stretch lens -> increase focal length (less convex) -- decrease lens power - 22Concave parabolic mirrors - light rays parallel to mirror's principal axis reflect @ single focal point -> usually forms real image Applications of concave mirrors: focusing sunlight @ water / direct car headlights towards roadPoint of curvature (c) = 2*f
Concave parabolic mirrors follow same image properties as convex lens (except real vs virtual image works opposite); vice versa for convex mirrors <-> divergent lens
Specular vs diffuse surface: smooth surface vs unsmooth (not mirror) - 23Least time principle of light: takes path of shortest time possible between mediums Refractive index = speed of light @ vacuum ./. speed @ medium Dispersion happens because refractive index depends on wavelength (greater refractive index -- smaller wavelength).
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- None Part 4-5 FlashCards sobre 4D, criado por Andrew Susilo em 07-12-2022.
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- Andrew Susilo
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