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

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The discussion clarifies the distinction between wave functions E(x,t), E(t), and E(x). E(x,t) represents the wave's behavior in both space and time, while E(t) indicates the wave's value over time at a fixed spatial point, and E(x) shows the wave's value at a specific time across different spatial points. The example of water waves illustrates these concepts effectively, emphasizing that E(t) and E(x) are not interchangeable but rather represent different aspects of wave behavior. Misuse of these notations in literature often leads to confusion, particularly when derivatives are involved.

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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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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.
 
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...
 

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