E - Nuclear and quantum physics, greenhouse effect

Activity (A)

of a radioactive sample is the number of decays per unit time.

Alpha decay

an unstable nucleus emits an alpha particle, which is essentially a helium nucleus made up of two protons and two neutrons (²₄He).

Beta minus decay

a neutron in the nucleus is converted into a proton, emitting an electron (β−) and an antineutrino (ν¯):

n→p+e^-+ν¯

Beta plus decay

a proton is converted into a neutron, emitting a positron (β+) and a neutrino(ν):

p→n+e⁺+ν

Binding energy

the energy required to hold the nucleus together.

Black body

an idealized object that absorbs all radiation falling on it and emits radiation based on its temperature.

Decay constant (λ)

measures how quickly a radioactive substance decays. It is defined as the probability of decay per unit time for a single nucleus.(λ=h/p)

Distance of closest approach

the minimum distance an alpha particle can reach during a head-on collision with a nucleus. This distance is determined using energy conservation.

Emission spectrum

the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule transitioning from a high energy state to a lower energy state.

Emissivity (e)

measures how efficiently a surface radiates energy compared to an ideal black body.

Gamma decay

an excited nucleus releases excess energy by emitting a gamma ray, a high-energy photon.

Induced fission

a nucleus splits after absorbing a neutron.

Luminosity (L)

the amount of radiated electromagnetic energy per unit time.

Nuclear fusion

the process where two light atomic nuclei combine to form a heavier nucleus, releasing an extraordinary amount of energy.

Parallax Angle

half the total angular shift of the star.

Photoelectric effect

the emission of electrons from a metal surface when light or other electromagnetic radiation shines on it.

Photon

a tiny particle that comprises waves of electromagnetic radiation.

Radiation

the transfer of thermal energy through electromagnetic waves, without the need for a medium.

Radioactive decay

the process by which an unstable atomic nucleus loses energy by radiation.

Solar constant (S)

the average intensity of solar radiation received at the top of Earth’s atmosphere, measured perpendicular to the incoming rays.

Spontaneous fission

a heavy nucleus splits into smaller nuclei without any external influence.

Stellar Parallax

the apparent shift in the position of a nearby star against the background of distant stars when observed from two opposite points in Earth’s orbit around the Sun, six months apart.

The half-life (T_1/2)

the time it takes for half of the radioactive nuclei in a sample to decay.

The strong nuclear force

is responsible for holding the nucleus together. It acts between all nucleons (protons and neutrons).

The work-energy theorem

the net work done on an object is equal to the change in its kinetic energy. (E=mc²)

The threshold frequency (f_c)

the minimum frequency of light required to eject electrons.