Understanding wavelength and frequency.

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    Frequency Wavelength
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Discussion Overview

The discussion centers on the relationship between wavelength and frequency of light as it transitions between different media. Participants explore the implications of this relationship, particularly the assertion that frequency remains constant while wavelength changes, and seek to understand the underlying principles and reasoning behind this phenomenon.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that when light enters a different medium, its frequency remains the same while its wavelength changes, leading to confusion regarding the inverse relationship between frequency and wavelength.
  • Others reference the equation wavelength * frequency = speed, suggesting that if frequency is constant and wavelength changes, then the speed of light must also change in different media.
  • One participant questions why it cannot be the case that frequency changes while wavelength remains the same, expressing curiosity about the factors that determine each property.
  • Another participant introduces the idea that the energy of light is proportional to frequency, implying that energy conservation necessitates a change in wavelength when entering a new medium.
  • A participant attempts to visualize the concept using a diagram from Wikipedia, indicating difficulty in conceptualizing how frequency can remain constant while wavelength changes.
  • One participant explains that frequency is a count of cycles, using an analogy of birds flying through a window to illustrate that the rate of cycles must remain consistent across boundaries.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and curiosity about the relationship between frequency and wavelength, with no consensus reached on the reasons behind the observed behavior of light in different media. Multiple competing views and questions remain unresolved.

Contextual Notes

Participants highlight the need for further clarification on the definitions and implications of frequency and wavelength, as well as the conditions under which these properties change. There is an acknowledgment of the experimental nature of the claims regarding light behavior.

sphyics
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"when light enters from one medium to other its frequency remains same whereas wavelength changes."
i'm not able to understand this relation as frequency has a inverse relation to wavelength
please help me to understand it thoroughly.
 
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Yes, but what IS the relation between frequency and wavelength?
Have you looked at the formula?
 
f95toli said:
Yes, but what IS the relation between frequency and wavelength?
Have you looked at the formula?

frequency is inversely proportional to wavelength
and that's where my problem is if wavelength changes how come the frequency remains constant.
 
wavelength * frequency = speed

If frequency remains the same and wavelength changes, then speed must change (this isn't a statement of causality, it's just a look at the equation). Light has different speeds in different mediums so it makes sense that it could change.
 
Last edited:
DocZaius said:
wavelength * frequency = speed

If frequency remains the same and wavelength changes, then speed must change (this isn't a statement of causality, it's just a look at the equation). Light has different speeds in different mediums so it makes sense that it could change.

i understand, why can't it happen other way frequency changes and wavelength remains same. (and this is what i was pondering about :))
 
Last edited:
sphyics said:
i understand, why can't it happen other way frequency changes and wavelength remains same. (and this is what i was pondering about :))

Good question! I would be interested in the answer too. I have learned that frequency is determined by the source and wavelength by the medium, but I have not learned why each of those properties are tied to each of those factors.
 
Well, one "handwaving" argument is that the energy of light is proportional to frequency (E=h*f) and since energy has to be conserved it is the wavelength that must change.

I am sure one can think of a simpler reason, but this is probably as good as any.

Also, remember that -as with everything in physics- this is ultimately an experimental fact, we do know that light travels at different speed in different media, and we also know the if we send in a wave with a given frequency into a medium the wavelength changes whereas the frequency does not.
 
i was jus trying to picturise the statement
"when light enters from one medium to other its frequency remains same whereas wavelength changes."
http://en.wikipedia.org/wiki/Frequency see the first right hand diagram titled
"Sinusoidal waves of various frequencies; the bottom waves have higher frequencies than those above. The horizontal axis represents time."

by using defeniton of wavelength (one crest & one trough) I'm not able to conceptualize the idea of frequency remaining same and wavelength changes.
 
The reason the frequency has to be constant when crossing a boundary is because a frequency is a count of individual events, which are, in this case, cycles. It's like if you have birds flying through an open window at a rate of ten per minute, that rate as counted from the outside and that rate as counted from the inside have to be the same.
 

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