ALevel物理量子和核子考点分析

2020-05-25 2135浏览

　　ALevel考试科目众多，ALevel物理就是其中最热门的科目之一，很多考生在选课的时候都会选择物理考试，在物理备考之中，量子和核子是非常核心的考点，下面小编就为大家分析这两大考点，希望能够帮助到大家！

　　一.the definition of key vocabularies.

　　-Particle model: objects that are hard, have mass and move about according to laws of Newtonian mechanics

　　-Wave model: shaped like a sine graph, do not have mass or charge. Their defining characteristics are diffraction and interference

　　-Photoelectric effect: when an electromagnetic radiation of sufficiently high frequency falls on a metal surface, electrons are emitted and the emitted electrons are called photoelectrons

　　-Photoelectric current: current due to photoelectrons

　　-Photon: each quantum (particle) of electromagnetic radiation

　　-Work function: minimum amount of energy required by an electron to escape its surface

　　-Matter wave: a moving particle of matter of momentum will have an associated wave of wavelength where

　　-Under normal conditions, an atom is in its ground state where it posses the minimum possible energy

　　-Transition: shifting of electrons between energy levels

　　-Mass defect : the difference between the total mass of the individual, separate nucleons and the mass of the nucleus

　　-Binding energy : the minimum external energy required to separate all the neutrons and protons of a nucleus. It is also the energy released when the nucleus is assembled from its constituent nucleons

　　-Binding energy per nucleon of a nucleus is the ratio of the total binding energy to its nucleon number

　　-Fission: process in which a massive nucleus splits to form two smaller fragments-Fusion: process by which two very light nuclei join together to form a heavier nucleus

　　-Random: impossible to predict and each nucleus has the same probability of decaying per unit time

ALevel物理量子和核子考点分析

　　-Spontaneous: not affected by external factors such as the presence of other nuclei, temperature and pressure

　　-The activity of a radioactive sample is the rate at which nuclei decay or disintegrate

　　-The decay constant is the probability that an individual nucleus will decay per unit time interval

　　-The half life of a radioactive is the mean time taken for half of the active nuclei in a sample to decay

　　二. Key rules

　　Laws of Photoelectric Emission:

　　• 1st Law: number of photoelectrons emitted per second is directly proportional to intensity of incident radiation

　　• 2nd Law: max kinetic energy of photoelectrons is directly proportional to the frequency of the incident radiation but independent of its intensity

　　• 3rd Law: for every metal, there is a minimum frequency of incident radiation below which photoelectric emission does not take place; threshold frequency

　　• Threshold frequency: minimum frequency required to release electrons from the surface of a metal

　　三. important formula needed to do calculation