Uplearn electromagnetic radiation from stars

Quantised

energy levels exist in discrete values

Why are energy levels in an atom negative?

The electrons bound to the atom must gain energy in order to move up to a higher energy level or escape the atom, therefore we write that they have negative energy

The electron has been excited

It has gained sufficient energy to move from one energy level to another that is at a higher energy

electronvolt

The electronvolt is the amount of energy transferred to an electron when it is passed through a potential difference of one volt

An electron undergoes de-excitation within an atom. What happens to the energy it loses?

It is released as a single photon

Luminosity

total radiant power output of a star, measured in W

Hertzsprung-Russell diagram

a graph of log ( L / Lsolar) on the y-axis and log(T) on the x-axis. The log(T) axis runs from high values on the left to low values on the right

Electron energy level

a discrete energy that an electron in an atom is allowed to possess. Energy levels in atoms are negative

Ground state

the lowest electron energy level of an atom

The wavelengths of light emitted by an atom form a unique pattern called an:

• Emission spectrum or emission spectra

Which of the following is an emission spectrum?

1)Which of the following might be produced by heated metal such as a filament lamp?

2)What is this type of spectrum called?

1) B

2)continuous spectrum

1)Which of the following might be produced by continuous spectrum passing through a cool gas?

2)What is this type of spectrum called?

1)A

2)absorption spectrum or absorption spectra

Absorption spectra are used to study stars. They can be used to:

Identify the elements within a star

Emission spectrum

A set of electromagnetic frequencies produced by excited atoms and visible as bright lines in spectroscopy. Each atom has a characteristic emission spectrum that represents its unique set of energy levels

Continuous spectrum

A spectrum containing all visible electromagnetic frequencies are present, for example produced by a lamp filament or other heated solid metals

Absorption spectrum

A set of electromagnetic frequencies that are missing from an otherwise continuous spectrum and therefore show as dark lines on the spectrum. The missing frequencies have been absorbed and re-emitted in all directions by atoms or molecules present in between the source and detector. The absorbed frequencies correspond to the energy levels present in the absorbing atoms or molecules