Concept explainers
(a)
The graph for the intensity curve of a blackbody having a temperature of
(a)
Answer to Problem 36Q
Solution:
Explanation of Solution
Introduction:
Wien’s law: Objects at different temperatures emit a spectrum that peaks at different wavelengths.
Explanation:
According to Wien’s law, wavelength is inversely proportional to temperature, so objects at different temperatures emit a spectrum that peaks at different wavelengths.
Now, as the wavelengths of the spectrum are different, the colors associated with those wavelengths will be different as well.
The intensity curve is plotted by representing wavelength on the horizontal axis and intensity on the vertical axis. So, for a temperature of
The curve will peak at around
The blackbody will appear red in color because the intensity of the
According to the above graph, the maximum intensity is for the red color, so the blackbody will appear red in color to us.
Conclusion:
The sketch shows that for a temperature of
(b)
The graph for the intensity curve of a blackbody having a temperature of
(b)
Answer to Problem 36Q
Solution:
Explanation of Solution
Introduction:
Wien’s law: Objects at different temperatures emit a spectrum that peaks at different wavelengths because the wavelength is inversely proportional to the temperature.
Explanation:
According to Wien’s law, objects at different temperatures emit a spectrum that peaks at different wavelengths.
As the wavelengths of the spectrum are different, the colors associated with those wavelengths will be different as well.
The intensity curve is plotted by representing wavelength on the horizontal axis and intensity on the vertical axis.
So, for a temperature of
The curve will peak at around
The black body will appear blue in color because the intensity of the radiation emitting from the blackbody is peaking at a shorter wavelength. The human eye can sense red, green, and blue colors.
According to the graph above, the maximum intensity is for the blue color, so the blackbody will appear blue in color to us.
Conclusion:
The sketch shows that for a temperature of
(c)
To explain: The reason behind color ratios
(c)
Answer to Problem 36Q
Solution:
For a relatively hot star, the value of brightness is in order
So, the ratios
Explanation of Solution
Introduction:
When a hot star is observed through the U (ultraviolet), V (yellow and green), and B (blue) filters, the intensity of the U filter will be higher than that of the B filter, and will be the dimmest when observed through the V filter.
Similarly, when a cold star is observed through U, V, and B filters, the intensity will be higher through the V filter than through the B filter, and it will be dimmest through U filter.
Explanation:
For a star of temperature
So, the value of the ratios
For a star of temperature
So, the value of the ratios
Conclusion:
Hot stars appear to be blue in color and cold stars appear to be red.
This is why when a hot star is observed through a B filter, the intensity is highest and similarly, when a cold star is observed through a V filter, the intensity is highest.
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Chapter 17 Solutions
Universe
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