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Based on my understanding, frequency is dependent on the number of times that the wave passes through the resting point, and therefore the frequency is the speed of the wave. That makes sense to me. The thing that's tripping me up is that frequency is inversely proportional to wavelength, and the color of, for example, a laser, is shown by the wavelength of the output of the diode.

I don't understand how a laser of a higher wavelength would be traveling at the same speed as a laser of a lower wavelength since a different wavelength would change the frequency. Another thing I'm confused about is that light "doesn't have a color", but you can buy a light that shines a certain color, or a laser that shines red as opposed to cyan.

What am I missing?

ECThunderation
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2 Answers2

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Wave speed is $f\lambda$

$c=f\lambda$

If the frequency increases, the wavelength decreases

Frequency is how frequent a peak travels across a certain point ( or freq of osscilations), if the frequency is increased, with a constant wavelength, then the same distance is covered in a shorter time making the wave speed up. So if the wavelength decreases, a shorter distance is traveled, in a higher time. Balancing out the change in frequency, causing the speed to be constant

jensen paull
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A wave is characterized by its amplitude $A$, frequency $\nu$, wavelength $\lambda$, and speed $v$. Stand at a certain point and allow the wave to travel past you. The amplitude is the height you measure between the highest and lowest intensity of the wave. Frequency is the rate that the signal oscillates between the highest and lowest intensity. For light, frequency defines the energy in the wave as $E = h\nu$, where $h$ is Planck's constant. Now run along side the wave until you see no oscillations in intensity. You are traveling at the speed of the wave. Determine the wave length by taking the frequency that you found when standing still and the speed when you moved with the wave using the equation $v = \lambda \nu$.

If you do this experiment in vacuum, you will find that $v = c$, the speed of light. If you do this experiment in anything other than vacuum, you will find that $v = c/n$, where $n$ is the index of refraction for the medium. The frequency of the light will not change between vacuum and any other medium. The wavelength will change (decrease) according to $\lambda_{n} = \lambda_{1} / n$, where $\lambda_n$ is the wavelength in the medium and $\lambda_1$ is the wavelength in vacuum.

Visible light is a combination of all frequencies (colors) of light. We select (pull out) frequencies (colors) using such objects as prisms.

Jeffrey J Weimer
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