Modern Physics and The Atom

These flashcards cover key concepts related to modern physics, the photoelectric effect, atomic structure, and nuclear properties.

Captive reactance

The opposition that a device offers to the flow of alternating current due to its inductance.

Inductive reactance

Denoted as $X_L$, it is given by the formula X_L = rac{V}{I} where $V$ is the voltage and $I$ is the current.

Impedance

Represented as $Z$, impedance is the total opposition that a circuit presents to alternating current, calculated as Z = rac{V}{I}.

Photon energy

The energy of a photon is given by the equation E = h
u = rac{hc}{ ext{λ}}.

Photon momentum

The momentum of a photon can be calculated using the formula p = rac{h}{ ext{λ}} = rac{E}{c}.

Max. KE of ejected photo-electron

Calculated as $K_{max} = E - ext{φ}$, where $E$ is the energy of the incoming photon and $ext{φ}$ is the work function.

Threshold frequency

The minimum frequency, $<br /> u_0$, required to eject photoelectrons, given by
u_0 = rac{ ext{φ}}{h}.

Stopping potential

The potential needed to stop the most energetic photoelectrons, denoted as $V_s$.

Population at time t

Represents the number of particles remaining at time $t$ and is given by $N = N_0 e^{- ext{λ}t}$.

Half-life

The time required for half of the radioactive nuclei in a sample to decay, denoted as t_{1/2} = rac{0.693}{ ext{λ}}.

Average life

The average lifetime of particles, calculated as au = rac{1}{ ext{λ}}.

Mass defect

The difference between the total mass of individual nucleons and the mass of the nucleus, given by $ext{Δm} = [Z m_p + (A - Z) m_n] - M$.

Binding energy

The energy required to separate a nucleus into its individual nucleons, represented as $B = [Z m_p + (A - Z) m_n - M] c^2$.

Q-value

The energy released in a nuclear reaction, calculated as $Q = U - V$.

de Broglie wavelength

The wavelength associated with a particle, calculated using ext{λ} = rac{h}{p} where $p$ is the momentum.

Energy in Bohr's orbit

The energy of an electron in Bohr’s orbit is given by E_n = -rac{13.62 ext{ eV}}{n^2}.

Radius of the n-th Bohr’s orbit

Given by the formula $r_n = n^2 imes 0.529 ext{ Å}$.

Quantization of angular momentum

States that angular momentum is quantized as L = nrac{h}{2 ext{π}}.

Absorption

The process in which an electron absorbs energy and moves to a higher energy state.

Wavelength of emitted radiation

The wavelength for the transition from state $n_2$ to state $n_1$ is given by the energy difference divided by Planck's constant.

Moseley's law

A law that relates the wavelengths of X-ray emissions to atomic number, given by the equation $<br /> u = a(Z - b)$.

Heisenberg uncertainty principle

A fundamental limit on the precision of simultaneously measuring pairs of physical properties, often stated as ext{Δx} ext{Δp} ext{≥} rac{h}{2}.

Nuclear radius

The radius of a nucleus, approximated by the formula $R = R_0 A^{1/3}$ where $R_0 = 1.1 imes 10^{-15} m$.

Decay rate

The rate at which a radioactive substance transforms, represented by the symbol A = -rac{dN}{dt}.

Transconductance

A parameter that indicates the output current changes per unit input voltage in a transistor, denoted as $g_m$.

Amplification by a triode

The process whereby a triode increases signal power, represented by $A = g_m R_{load}$.