Wave conventions: E(x,t) and E(t), E(x) confusion

In summary, the conversation discusses the function E(x,t) as a fundamental description of a wave, with E(t) being an envelope function and E(x) being a snapshot of the wave at a fixed time. E(t) describes how the wave varies over time at a fixed point, while E(x) describes how it varies with position at a fixed time. The use of both E(x) and E(t) can be confusing and lead to taking derivatives with respect to both x and t.
  • #1
betelgeuse91
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I understand that waves are function of space and time in nature, so E(x,t) will be fundamental description of a wave. I notice that often people denote a wave as E(t) for instance, an envelop function of a pulse. For this case, E is an oscillation at a fixed spatial point x? So that the point x moves up and down as the wave passes through it in time?
And for E(x) this is a snap shot picture of the wave at some time t? This is easier to see (although i don't know if I understand it correctly)
Well then can I treat E(x) and E(t) as like... same quantity in some sense?
Like for example, when I read a Gaussian envelope E(t), then I image the pulse to be Gaussian in space at some point in time...

Thanks for help!
 
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  • #2
betelgeuse91 said:
So that the point x moves up and down as the wave passes through it in time?
No, when we write ##E(t)## we're looking at the value of ##E## over time at some fixed point ##x##. Water waves (with ##E## being the depth of the water) are an example: we can describe the wave with the function ##E(x,t)## which tells us what depth we'd find if we drop a measuring buoy into the water at point ##x## and time ##t##; or we can use the function ##E(t)## which tells us how the depth reported by a measuring buoy tethered at some fixed location will vary over time.
And for E(x) this is a snap shot picture of the wave at some time t? This is easier to see (although i don't know if I understand it correctly)
That is correct. Just as ##E(t)## tells us how ##E## varies over time at some fixed point, ##E(x)## tells us how ##E## varies with position at some fixed time.
 
  • #3
Nugatory said:
No, when we write ##E(t)## we're looking at the value of ##E## over time at some fixed point ##x##. Water waves (with ##E## being the depth of the water) are an example: we can describe the wave with the function ##E(x,t)## which tells us what depth we'd find if we drop a measuring buoy into the water at point ##x## and time ##t##; or we can use the function ##E(t)## which tells us how the depth reported by a measuring buoy tethered at some fixed location will vary over time.
That is correct. Just as ##E(t)## tells us how ##E## varies over time at some fixed point, ##E(x)## tells us how ##E## varies with position at some fixed time.

Ahh... right. Thank you for clarification. In literature, people confusingly use E(x) and E(t) and take derivatives with respect x and t which drives me crazy...
 

1. What is the difference between E(x,t) and E(t)?

E(x,t) represents the electric field at a specific point in space and time, while E(t) represents the electric field at all points in space at a specific time.

2. Why is there confusion between E(x,t) and E(t)?

There can be confusion between E(x,t) and E(t) because they both represent the electric field, but at different levels of specificity. E(x,t) is more specific as it represents the electric field at a particular point, while E(t) is more general as it represents the electric field at all points.

3. Can E(x) and E(t) be used interchangeably?

No, E(x) and E(t) cannot be used interchangeably. E(x) represents the electric field at a specific point in space, while E(t) represents the electric field at a specific time. They are not equivalent and cannot be used interchangeably.

4. How are E(x,t) and E(t) related?

E(x,t) and E(t) are related as E(t) is the time average of E(x,t) over all points in space. This means that E(t) is the average electric field at all points in space at a specific time, while E(x,t) is the electric field at a specific point in space and time.

5. What are some examples of when E(x,t) and E(t) are used?

E(x,t) is commonly used in analyzing the electric field of a specific point charge or in a specific region of space. E(t) is often used in analyzing the electric field of electromagnetic waves, which vary in time but are uniform in space.

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