The Student Room Group

Waves

Nodes carry no energy

can someone explain this to me?
Infact, i might be able to :smile:
The nodes are the points on the wave with the least amplitude. This means they have the least displacement and therefore they have the least energy.
On the other hand, anti nodes have the most amplitude, and therefore carry the most energy :smile:

Spoiler

This shows the nodes and antinodes on the wave, the nodes always have the least amplitude (usually 0) and therefore have no movement, no movement is no kinetic energy etc.
(edited 7 years ago)
Reply 2
Original post by The-Spartan
Infact, i might be able to :smile:
The nodes are the points on the wave with the least amplitude. This means they have the least displacement and therefore they have the least energy.
On the other hand, anti nodes have the most amplitude, and therefore carry the most amplitude :smile:

Spoiler

This shows the nodes and antinodes on the wave, the nodes always have the least amplitude (usually 0) and therefore have no movement, no movement is no kinetic energy etc.


where does this come from? i understand the least displacement and amplitude but i don't see where energy comes into this.

is there an equation which explains this?
Original post by thefatone
where does this come from? i understand the least displacement and amplitude but i don't see where energy comes into this.

is there an equation which explains this?


Ke=1/2 mv^2. Therefore if the rope isn't moving (which is the case of a node) the kinetic energy of the wave at that point is 0 as the velocity is 0
Reply 4
Original post by samb1234
Ke=1/2 mv^2. Therefore if the rope isn't moving (which is the case of a node) the kinetic energy of the wave at that point is 0 as the velocity is 0


do waves have kinetic energy????
Original post by thefatone
do waves have kinetic energy????


Yes
Reply 6
Original post by samb1234
Yes


how???? i understand the particle nature of the em spectrum as demonstrated by the photoelectric effect but how to waves transfer energy?
Original post by thefatone
how???? i understand the particle nature of the em spectrum as demonstrated by the photoelectric effect but how to waves transfer energy?


Well the string is moving right? therefore if it is moving it must have a kinetic energy. The derivation of the exact energy of a wave goes way beyond this level
Original post by thefatone
how???? i understand the particle nature of the em spectrum as demonstrated by the photoelectric effect but how to waves transfer energy?


Em waves don't have kinetic energy. Waves like sound waves do.
Reply 9
Original post by samb1234
Well the string is moving right? therefore if it is moving it must have a kinetic energy. The derivation of the exact energy of a wave goes way beyond this level


the string is a materialistic thing whereas a wave is not
Original post by thefatone
the string is a materialistic thing whereas a wave is not


Certain waves involve displacing matter. E.g. a wave in water, the water has energy from this wave like motion. In the circumstance of a wave in water the higher the displacement then the more EK there is.
Original post by thefatone
the string is a materialistic thing whereas a wave is not


The wave is travelling through the string
Reply 12
Original post by Vikingninja
Certain waves involve displacing matter. E.g. a wave in water, the water has energy from this wave like motion. In the circumstance of a wave in water the higher the displacement then the more EK there is.

I see so the waves transfer energy by displacing other stuff? so would those be classed as mechanical/longitudinal waves?
Original post by samb1234
The wave is travelling through the string


yes thus the wave isn't materialistic, yes it acts through the string
Original post by thefatone
I see so the waves transfer energy by displacing other stuff? so would those be classed as mechanical/longitudinal waves?


yes thus the wave isn't materialistic, yes it acts through the string


A mechanical wave is where matter is oscillating so yes, a EM wave wouldn't be this. Mechanical waves can be transverse or longitudinal. Example of transverse is a water ripple/wave and a longitudinal one would be a sound wave. A sound wave works by knocking particles into each other and transferring their EK.
Original post by Vikingninja
A mechanical wave is where matter is oscillating so yes, a EM wave wouldn't be this. Mechanical waves can be transverse or longitudinal. Example of transverse is a water ripple/wave and a longitudinal one would be a sound wave. A sound wave works by knocking particles into each other and transferring their EK.


water waves aren't a great example for this, they are a combination of both which might confuse things further
Reply 15
Original post by Vikingninja
A mechanical wave is where matter is oscillating so yes, a EM wave wouldn't be this. Mechanical waves can be transverse or longitudinal. Example of transverse is a water ripple/wave and a longitudinal one would be a sound wave. A sound wave works by knocking particles into each other and transferring their EK.


i guess what i'm really asking is how this happens... which is probably way beyond my level. ;( :cry2:
Original post by thefatone
i guess what i'm really asking is how this happens... which is probably way beyond my level. ;( :cry2:

This gif shows how they knock into each other and rebound.



In a collision between two particles, EK is transferred.
(edited 7 years ago)
Reply 17
Original post by Vikingninja
This gif shows how they knock into each other and rebound.



In a collision between two particles, EK is transferred.


i see ok thanks at leats there's 1 thing i understood.....

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