1.6 using radiation to investigate stars

Question 1

what are emission line spectra and how are they formed?

Answer 1

• a series of coloured lines on a black background
• when light passes through the outer layers of a star, the electrons in the atoms absorb photons and become excited. they then de-excite, releasing photons of specific wavelengths. these photons are detected on Earth and have wavelengths characterised of the elements in the outer layers.

Question 2

what are continuous line spectra

Answer 2

all visible wavelengths of light are present.
comes from the dense gas of the surface of a star

Question 3

absorption line spectra

Answer 3

• a series of dark line against the background of the continuous spectrum, with each line corresponding to a wavelength of light
• light absorbed by atoms in the outer layers of a star. the dark lines are at wavelengths that are characteristic of the elements in the outer layers

Question 4

black body

Answer 4

a perfect absorber and emitter of EM radiation - it absorbs all EM radiation incident upon it
e.g. stars

Question 5

Wien’s displacement law

Answer 5

the wavelength of emitted radiation at peak intensity is inversely proportional to the temp of the black body

Question 6

Stefan’s law

Answer 6

the power output of a star is directly proportional to its surface area and to its (absolute temp)^4

Question 7

multiwavelength astronomy

Answer 7

using different wavelengths of EM radiation to observe the universe.

Question 8

black body graphs

Answer 8

• the higher the temp, the higher the peak intensity
• wavelength peak is shifted to the left at higher temps
• the lower temp, the longer the flat section before it lifts off

Question 9

what colour are the hottest blackbodies

Answer 9

blue

Question 10

luminosity of a star

Answer 10

the total energy it emits per unit time in the form of EM radiation