1. Mechanical waves are periodic disturbances in a medium that transfei energy 2.electromagnetic waves donot need a medium for propagation 3.waves can be either transverse or longit
udinal 4.the velocity of a wave is equal to the the product of its frequency and its wavelength 5.inference and diffraction are characteristics typical for all waves 6.resonance involves matching the natural vibrating vibrating frequency of objects 7.nodes are points that do not move in a standing wave 8.standing wave node occur every half wavelength . 9.diffraction occurs as waves bend around barriers in the same medium 10.interference can either be constructive (reinforce) or destructive(cancellation) 11.superposition is the mixing of waves , which can either add or subtract amplitudes depending on the phases of the interfering waves. Doppler effect Laws of vibrating strings Vibrating air columns (closed pipes open pipes )
The number of beats=the difference between the two frequencies
Geometrical optics: Reflection and Refraction
Normal 法线 incident light 入射光线 diffuse reflection 漫反射 regular reflection 镜面 反射 erect 正立的 center of curvature (C) 两倍焦距 principal focus (F) f=C/2 1.light is an electromagnetic wave 2.The law of reflection states that the angle of incidence is equal to the angle of reflection. 3.All angle are measures relative to the normal line. 4.Refraction is a change in the direction of light caused by a change in light’s velocity as it goes from one transparent medium into another at an oblique angle. 5.The absolute index of refractionof a transparent material is equal to the ratio of the velocity of light in air to the velocity of light in the material. 6.As light goes form a lower-index material to a high-index material, it slows down and bends toward the normal. 7.n1 *sinθ 1=n2*sinθ 2 8.Total reflection occurswhen the angle of the incidence in the optically denser medium is grater than the critical angle(one condition is must n1:n2>1) 9.Real image can be projected onto a screen. Vitul images cannot be projected and are percieved by the brain as existing on the other side of a mirror. 10.Real images can be formed by concave mirror or convex lenses. 11.A prism can disperse white light into the colors of the spctrum since the different frequencies of light refract at different angle in the prime.
13. The color of an opaque object is determined by the color of the light it reflects. 14. Types of spectra Table(2)
15. Convex lens converg; concave lens diverg. 16. 1/do+1/di=1/f 17. Size of the image/size of object=image distance /object disance=magnification(m) 18. Image in palne mirror (1) the image is the same size.(2)the image is erect(3)the image is virtual.
Physical optics Interference and diffraction
Light and interference diffraction of light by a grating Thin film interference polarization 1.Thomas Young demonstrated light interference in 1801 2.Interference colors can be seen in thin films and soap bubbles 3.The polarization of light is evidence for its transverse nature. Longitudinal waves(such as sound)cannot be polarized. 4.POLARIZATION 原理
Elements of electronics
1.capacitors store charge in simple circuits. 2.Heated metals can emit electrons. 3.In a vacuum tube, a hot filament emits a beam of electrons that can be controlled by electromagnetic field and potential differences. 4.Q=CV C (farad) 5.Potential energy = 6.In series 7.In parallel 8.Thermionic emission:heated metal the part that is heated so that it will give off electrons is called the cathode.
1.electric charge are positive or negative 2.Coulomb’s law is described as an inverse square law for static charges. 3.Electric field lines show the direction that a positive test charge would travel.(?) 4.The electrical potential difference (voltage)is a measure of the work done per unit charge 5.Conventional current indicates the flow of positive charge una circuit. 6.Ohm’s law related the voltage in a circuit to the current and electrical resistance. 7.Seried circuit have the same current throught,but the potential drops are shared proportionally among the various resistors. 8.Parallel circuits have the same potential diffence across each resistor,but the current is divided along the circuits inversely proportional to amount of resistabce in a branch. 9.Kirchhoff’s rule says that the sum of the currents entering a branch must equal to the sum of the currents leaving a branch in a parallel circuit. 10.Joule’s law Q= 11.Power P=VI 12.The combined resistors in parallel is always less than the smallest resistance. 13.The internal resistance can be treated as anexternal resistance VT=emf-Ir 14.Resistance(ohm) R=kL/A metallic is increase when temperature rises 15.Conductivity is the reciprocal of resistivity
10.the field lines around terrestrial magnets flow from north to south as indicated by a magnetic compass 11.An electric current can generate a magnetic field 12.The direction of electromagnetic field can be determined using right-hand rules 13.Interacting electromagnetic fields can produce forces in current-carrying wires or on moving electric charges 14.An electric meter (voltmeter or ammeter)can be develped based on the twisting force on a wire caused by interacting electromagnetic field. 15.A wire moving in a magnetic field can have a current induced in it. 16.The magnetic flux of a current induced in a wire always opposes the magnetic flux of the current that induces it. The Lenz’s law. 17.secondary emf/primary emf=number of turns on secondary/number of turns on primary 18.VsIs=VsIs*efficiency
Quantum theory and nuclear phsics
Photoelectric effect nuclear changes atomic models subatomic particles and accelerators fission and fusion radioactivity 1.photoelectric effect:(1)the light consist of photos (2)cannot be explained by the wave theory of light 2.The maximum kinetic enery of emitted electrons is independent of the intensity of the incident light but varies directly with the frequency of the incident light. 3.Plank’s constant (h) is a universal constant that governs the quantum models of light and atoms. 4. Bohr’s theorythe emission of hydrogen specrea by hypothesizing that electrons can exist in certain energy states. Light can be emitted as electrons go from higher to lower energy states. 5.Rutherford showed that the atom consistd mostly of empty space with a small,positively charged nucleus. 6.The instability of a nucleus profuces radioactive decay that can transmute one element into another. 7.Fission involves the splitting of a uranium nucleus,while fusion involves the combining fo hydrogen unclei to form helium.in both cases,large amount of energy are released,consistent with Einstein’s formula 8.Protons and neutrons are made up of even smaller particles called quarks.