Chapter 5: Problem 15
T/F: Cooler objects radiate more of their total light at shorter wavelengths than do hotter objects.
Short Answer
Expert verified
False
Step by step solution
01
Understand Blackbody Radiation
Blackbody radiation refers to the theoretical spectral distribution of electromagnetic radiation emitted by an object that absorbs all radiation that strikes it. The color and intensity of the light emitted depend on the object's temperature.
02
Apply Wien’s Displacement Law
Wien’s Displacement Law states that the wavelength at which the emission of a blackbody spectrum is maximized is inversely proportional to the temperature of the blackbody. The law is expressed as: \[\frac{\text{d}}{\text{d}λ}(λ^5(e^{(\frac{hc}{λkT})} - 1)^{-1}) = 0\] Thus, \[\text{λ}_{max} = \frac{b}{T}\] where \[\text{λ}_{max} \] is the peak wavelength, \[\text{T} \] is the temperature, and \[\text{b}\] is Wien's constant.
03
Relate Peak Wavelength to Temperature
According to Wien’s Displacement Law, the peak wavelength of radiation emitted by a cooler object is longer (i.e., redder) compared to a hotter object whose peak wavelength is shorter (i.e., bluer).
04
Conclude Based on Physical Laws
From the above steps, it follows that cooler objects do not radiate more of their total light at shorter wavelengths; instead, they radiate more at longer wavelengths. Therefore, the statement is false.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Wien’s Displacement Law
Wien’s Displacement Law is a crucial principle in understanding blackbody radiation. It relates the temperature of an object to the wavelength at which it emits the most radiation. According to this law, as the temperature of an object increases, the peak wavelength of the emitted radiation shifts to shorter wavelengths. This is expressed mathematically as: \(\text{λ}_{max} = \frac{b}{T}\), where \(\text{λ}_{max}\) is the wavelength of maximum emission, \(T\) is the absolute temperature in kelvins, and \(b\) is Wien's displacement constant (approximately 2.898 x 10^(-3) m⋅K). In simpler terms:
- Hotter objects emit radiation that peaks at shorter wavelengths (bluer light).
- Cooler objects emit radiation that peaks at longer wavelengths (redder light).
Electromagnetic Radiation
Electromagnetic radiation encompasses a wide range of wavelengths and frequencies of light, including visible light, radio waves, and X-rays. All objects emit electromagnetic radiation as a function of their temperature.
- At higher temperatures, the emitted radiation shifts to higher frequencies and shorter wavelengths.
- At lower temperatures, the radiation shifts to lower frequencies and longer wavelengths.
Temperature and Wavelength Relationship
The temperature of an object significantly influences its emitted radiation. Wien’s Displacement Law directly connects this: the higher the temperature, the shorter the wavelength of peak emission. For practical understanding:
- Hotter objects (like the Sun) emit most of their light at shorter wavelengths, such as visible or ultraviolet light.
- Cooler objects (like the Earth) emit most of their light at longer wavelengths, such as infrared.