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Scientists can analyse light from stars that has passed through a diffraction grating - Edexcel - A-Level Physics - Question 17 - 2023 - Paper 2
Question 17
Scientists can analyse light from stars that has passed through a diffraction grating. (b) A spectrum of the visible light emitted by a particular star is shown. (... show full transcript
Worked Solution & Example Answer:Scientists can analyse light from stars that has passed through a diffraction grating - Edexcel - A-Level Physics - Question 17 - 2023 - Paper 2
Step 1
Light interacts with atoms as it passes through the atmosphere of the star.
Answer
As light travels through the atmosphere of a star, it interacts with atoms present in that atmosphere. When photons encounter an atom, specific energies are absorbed that excite electrons, promoting them to higher energy levels. This process results in certain wavelengths of light being absorbed. The light that reaches the observer’s eyes will then have dark lines corresponding to these absorbed wavelengths in its spectrum, creating the characteristic absorption lines.
Step 2
On the axes below, sketch a graph of the intensity of radiation against the wavelength of that radiation for this star.
Answer
To sketch the graph:
- On the x-axis, label 'Wavelength / µm', ranging from around 0.1 to 2.
- On the y-axis, label 'Intensity'.
- Start with a curve peaking at around 0.5 µm, indicating the maximum intensity due to the star's temperature.
- Represent absorption lines by drawing dips in intensity at specific wavelengths where dark lines appear in the spectrum, indicating the wavelengths of absorbed light.
- Ensure that the general shape of the graph follows a black-body radiation curve, peaking at shorter wavelengths for a temperature of 5800K.
Step 3
This star is a main sequence star.
Answer
Main sequence stars are in a stable balance between gravitational forces and the pressure from core nuclear fusion. As they fuse hydrogen into helium, energy is produced that creates outward pressure. This pressure counters the inward pull of gravity, preventing the star from collapsing. At this stage, the force of gravity trying to compress the star is perfectly balanced by the outgoing pressure from the fusion reactions.