A-level物理学习中有很多基础性的概念，比如电流、电力等，其中，有一个很大的章节是关于量子物理和核子物理的。对于他们的概念，很多同学都会有些分不清楚，下面，锦秋小编将为大家详细介绍这两块的内容，让看过这篇文章的同学们能够在paper4中遇到此章节的题，有清晰的思路并且将分数稳稳拿住。

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

-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

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