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In the middle of the 20th century, there were two competing theories of the Universe - AQA - A-Level Physics - Question 4 - 2022 - Paper 4
Question 4
In the middle of the 20th century, there were two competing theories of the Universe. In 1964, electromagnetic radiation was observed coming from all directions in s... show full transcript
Worked Solution & Example Answer:In the middle of the 20th century, there were two competing theories of the Universe - AQA - A-Level Physics - Question 4 - 2022 - Paper 4
Step 1
the main predictions and evidence for the theory
Answer
One theory that could explain the observed electromagnetic radiation is the Big Bang Theory. This theory predicts that the universe began from a hot, dense state and has been expanding ever since. According to this theory, the electromagnetic radiation we observe today is a remnant of that initial event.
The graph in Figure 2 indicates a peak intensity of radiation, which corresponds to the cosmic microwave background (CMB) radiation, a key piece of evidence supporting the Big Bang Theory. This radiation is observed at a wavelength of approximately 2.7 mm, consistent with the predictions of the Big Bang model, as it predicts black body radiation with a temperature of about 2.7 K.
Step 2
a suitable calculation
Answer
A suitable calculation involves using Wien's Law, which relates the temperature of a black body to the wavelength at which it emits the most radiation. Wien's Law is given by:
where b is a constant approximately equal to 2898 µm K.
For the observed peak wavelength of 2.7 mm (or 2700 µm), we can rearrange the equation to calculate the temperature:
This calculation further supports the theory of the universe's origins as described by the Big Bang Theory and correlates with the observed CMB.