Understanding the Infrared Glow of Objects: Hotter is Not Always Brighter

In summary, the conversation discusses the statement that the color an object glows has nothing to do with how hot it is. As an object is heated, it glows more in the visible range and less in the infrared range. The question then presents a statement about the day and night sides of the Earth and their reflectivity and infrared glow. There is some debate about the accuracy of the statement, but it is concluded that the statement is not clear and may not be correct. Finally, the conversation discusses the blackbody spectrum and its relation to temperature and the amount of infrared radiation. It is concluded that the fourth answer choice is correct despite its ambiguity.
  • #1
shmijda
23
0

Homework Statement


Which statement is true?
The color an object glows has nothing to do with how hot it is.

As you heat an object, it glows more in the visible and less in the infrared.

The day side of the Earth reflects more light, but the night side glows brighter in the infrared.

You glow brighter in every wave length than a frozen body would.

Homework Equations


none

The Attempt at a Solution


Choice 1 is wrong, choice 2 appears to be right, choice 4 also seems right. Choice 3 is wrong
 
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  • #2
Science is not a democracy and "voting" for the right answers is ridiculous so a poll is not a good idea.

#1 I agree it's wrong
#2 You might want to this think through again
#3 Well since the day side GETS more light, I'd say, yeah, it reflects more light, but is that a property of the day side or a property of the incident light? I think the question is a poor one. In any case, do you think the day side glows brighter in the infrared? Is that why you consider this one wrong? (I would agree, by the way)
#4 if we're only talking about radiation as opposed to reflection I agree w/ you but it seems like another ambiguously worded question.
 
  • #3
phinds said:
Science is not a democracy and "voting" for the right answers is ridiculous so a poll is not a good idea.

#1 I agree it's wrong
#2 You might want to this think through again
#3 Well since the day side GETS more light, I'd say, yeah, it reflects more light, but is that a property of the day side or a property of the incident light? I think the question is a poor one. In any case, do you think the day side glows brighter in the infrared? Is that why you consider this one wrong? (I would agree, by the way)
#4 if we're only talking about radiation as opposed to reflection I agree w/ you but it seems like another ambiguously worded question.
For choice 2, as you heat an object, its wavelength becomes shorter i.e. less in infrared more in visible no?
 
  • #4
Perhaps you think "in the infrared / not in the infrared" is pure binary? Actually there is quite a range of infrared and as you heat up an object it moves TOWARDS the visible but until it starts to glow (faint orange) it isn't there yet and will be radiating more strongly but still in infrared, just in shorter wavelengths
 
  • #5
phinds said:
Perhaps you think "in the infrared / not in the infrared" is pure binary? Actually there is quite a range of infrared and as you heat up an object it moves TOWARDS the visible but until it starts to glow (faint orange) it isn't there yet and will be radiating more strongly but still in infrared, just in shorter wavelengths
Yes, but if it is at the range where it is about to be visible light, then wouldn't the statement be true?
 
  • #6
  • #7
shmijda said:
Yes, but if it is at the range where it is about to be visible light, then wouldn't the statement be true?
So your point of view is "eh ... it COULD be true. If I set up things just right, there might be a special case where it's true. SO ... by me, it's true. End of story"

Sounds more like a negotiation than a search for reality.
 
  • #8
phinds said:
So your point of view is "eh ... it COULD be true. If I set up things just right, there might be a special case where it's true. SO ... by me, it's true. End of story"

Sounds more like a negotiation than a search for reality.
No that's not my point of view I was just examining all possibilities because I don't know what the answer is but ok
 
  • #9
shmijda said:
Yes, but if it is at the range where it is about to be visible light, then wouldn't the statement be true?
You seem to be assuming the total amount of light radiated is constant with temperature. It's not.
 
  • #10
vela said:
You seem to be assuming the total amount of light radiated is constant with temperature. It's not.
Doesn't it increase with temperature?
 
  • #11
Yes. Did you look at the plots of the blackbody spectrum at different temperatures? Does the amount of IR radiation decrease with rising temperature?
 
  • #12
vela said:
Yes. Did you look at the plots of the blackbody spectrum at different temperatures? Does the amount of IR radiation decrease with rising temperature?
nope it rises
 
  • #13
shmijda said:
nope it rises
And what do you conclude from this, as regards your problem?
 
  • #14
phinds said:
And what do you conclude from this, as regards your problem?
I guess answer 4 is correct despite its ambiguity
 
  • #15
shmijda said:
I guess answer 4 is correct despite its ambiguity
Uh ... we were talking about question #2
 
  • #16
phinds said:
Uh ... we were talking about question #2
yep answer 2 must be false then from the black body spectrum
 
  • #17
shmijda said:
yep answer 2 must be false then from the black body spectrum
Good. Now you see why I suggested you might want to rethink your original answer.
 

Related to Understanding the Infrared Glow of Objects: Hotter is Not Always Brighter

1. Why do objects emit infrared radiation?

Objects emit infrared radiation because they have a temperature above absolute zero, meaning that their molecules are constantly in motion and therefore have kinetic energy. This energy is emitted in the form of electromagnetic waves, including infrared radiation.

2. How does the temperature of an object affect its infrared glow?

The temperature of an object directly affects the amount and wavelength of infrared radiation it emits. The hotter an object is, the more kinetic energy its molecules have, resulting in a higher amount of infrared radiation emitted. However, the wavelength of the radiation also changes with temperature, with hotter objects emitting shorter wavelength (higher energy) radiation.

3. Is hotter always brighter in terms of infrared radiation?

No, hotter is not always brighter in terms of infrared radiation. While hotter objects do emit more infrared radiation, the wavelength and distribution of the radiation can also affect its perceived brightness. For example, an object with a very high temperature may emit most of its radiation in shorter wavelengths, which are not visible to the human eye and may not be perceived as bright.

4. How does the material of an object affect its infrared glow?

The material of an object can affect its infrared glow in several ways. Different materials have different abilities to absorb and emit infrared radiation, so the type of material can affect the amount of infrared radiation that is emitted. Additionally, the texture and reflectivity of the material can also affect the distribution of the emitted radiation, making some objects appear brighter or dimmer in infrared than others.

5. Can infrared radiation be harmful to humans?

Infrared radiation is generally not harmful to humans in small doses. However, prolonged exposure to high levels of infrared radiation, such as from sources like the sun or certain industrial processes, can cause damage to the skin and eyes. It is important to limit exposure to infrared radiation and to use protective measures when necessary.

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