Chapter 11: Modern Physics

**Quanta**

the origin of the name of quantum mechanics

**Photon**

is a quantum of electromagnetic energy

**Photoelectric effect**

is an illustration of light that behaves like a steam of photons

**Photoelectrons**

are the released electrons

**Metal’s work function, ϕ**

is a certain amount of energy had to be imparted to an electron on the metal surface in order to liberate it

**Electronvolt (eV)**

is equal to the energy gained (or lost) by an electron accelerated through a potential difference of one volt

In terms of electronvolts, the value of Planck’s constant is

**Atomic Spectra**

the produced patterns of sharp lines when the light from a glowing gas, passed through a prism to disperse the beam into its component wavelengths

**Balmer formula**

**Electromagnetic radiation**

propagates like a wave but exchanges energy like a particle

**Wave function, Ψ**

is the mathematical probability that a particle will be measured to be at a particular position when the position is measured

**Theory of Relativity**

a theory that have two postulates: (1) The results of physical experiments will be the same in any non-accelerating reference frames, and (2) The speed of light is constant.

**Time dilation**

is the difference in the elapsed time as measured by two clocks

Length contraction

a phenomenon in which moving along with the object, measures will observe the object to have a different length compared in a different reference frame

**Nucleons**

collectively are protons and neutrons

**Atom’s atomic number**

the number of protons in a given nucleus (denoted *Z*)

**Neutron number**

the number of neutrons in a given nucleus (denoted *N*)

**Nucleon number**

also called **mass number i**s the total number of nucleons, *Z* + *N* (denoted *A*)

**Isotopes**

are nuclei that contain the same numbers of protons but different numbers of neutrons

**Mass defect Δ*****m***

the difference between the mass of any bound nucleus and the sum of the masses of its constituent nucleons

**Energy formula**

Binding energy

of the nucleus formula tells how strongly the nucleus is bound:

**Binding-energy-per-nucleon:**