Module 5 - 5.5.2 Electromagnetic Radiation From Stars Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Energy Levels (definition)

A

The specific energies that electrons can have when occupying specific orbits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Electrons can move to a higher/lower energy level by

A

absorbing/emitting energy in the form of em radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At low temperatures, most electrons will be in the — energy level

A

lowest (n=1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Excitation (definition)
De-Excitation (definition)

A
  • when an electron moves from a lower to a higher energy level by absorbing energy
  • when an electron moves from a higher to a lower energy level after releasing energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q
  • The energy released in de-excitation is emitted as …
  • emitted – can have …
  • larger energy transition = …
A
  • emitted as em radiation of a specific frequency depending on the difference in energy between the energy levels
  • emitted photons can have a range of wavelengths spanning the whole em spectrum
  • larger energy transition = longer wavelength of emitted photon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When an electron is infinitely far from the nucleus, its energy is

A

0 (electron is said to be free from the atom)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

As an electron moves towards the nucleus, its energy (2)

A
  • decreases below 0
  • it becomes confined within the atom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The value of an energy level is equal to

A

the amount of energy required to remove an electron from that energy level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The value of the lowest energy level is equal to

A

the amount of energy required to remove an electron from the atom (ionisation)
most negative value at the ground state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Chemical Composition of Stars (7)

A
  • fusion reaction in star’s core produced photons of em radiation
  • photons are constantly absorbed by atoms in gas
  • then re-emitted with many different frequencies
  • produces a continuous spectrum of wavelengths
  • each gas produce a unique pattern of spectral lines
  • due to the specific transitions between the element’s energy levels
  • can be used to determine the presence of certain elements within the star
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

A Continuous Spectrum (definition)

A

A spectrum that appears to contain all frequencies over a comparatively wide range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Continuous Spectra are produced from

A

hot dense sources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

An Emission Line Spectrum (definition)

A

The spectrum of frequencies of em radiation emitted due to the electron transitions from a higher energy level to a lower one within an atom of that element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Emission Line Spectra act as (3)

A
  • a fingerprint for an element
  • as each element produces a unique emission line spectrum
  • due to its unique set of energy levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

An emission line spectrum consists of (2)

A
  • a series of bright lines against a dark background
  • each line corresponds to a different wavelength of photon emitted by an electron transition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Emission Line Spectra are produced by

A

hot low pressure gases

17
Q

An Absorption Line Spectrum (definition)

A

The pattern of dark lines in a continuous spectrum from a light source and is caused by light passing through an absorbing medium such as a gas
- the dark lines represent the frequencies absorbed by a medium

18
Q

The Sun’s atmosphere produces a — line spectrum (3)

A
  • absorption
  • since it is not hot enough to produce an emission one
  • dark lines in the spectrum are caused by the presence of certain elements (e.g. H, He)
19
Q

Using a Transmission Diffraction Grating allows for (2)

A
  • more accurate measurements
  • since the angular dispersion of the colours will be much greater than using a prism
20
Q

Dispersion (definition)

A

The separation of visible white light into a spectrum of its colours

21
Q

Uses of Transmission Diffraction Gratings (2)

A
  • analyse light from stars
  • analyse the composition of a star
22
Q

The wavelength of em radiation emitted by an object depends on its

A

temperature

23
Q

The peak intensity of a star’s emission occurs at (3)

A
  • a specific wavelength (λmax) related to the star’s temperature
  • doesn’t mean it is the largest λ emitted by the star
  • as surface temperature increases peak occurs at a lower λ
24
Q

For a graph of intensity against λ, the area under the curve — as – increases (3)

A
  • increases drastically as temperature increases
  • since the area represents the total energy emitted by the body
  • which is strongly temperature dependent
25
Q

An Ideal Black Body (definition)

A

A body that absorbs and emits all wavelengths
(a theoretical object)

26
Q

Hotter objects tend to be (colour)
Cooler objects tend to be (colour)

A
  • white/blue
  • red/yellow
27
Q

Wien’s Law

A

λmax ∝ 1/T

28
Q

Stefan’s Law

A

The total energy emitted by a black body per unit area per second is proportional to the fourth power of the absolute temperature of the body

29
Q

If two stars have the same temperature, the star that appears brighter has the

A

larger diameter

30
Q

Difficulties in obtaining accurate results for Wien’s and Stefan’s Law (2)

A
  • Earth’s atmosphere only allows certain wavelengths of em radiation through
  • telescopes need to be placed at high altitudes to avoid dust and human light pollution