user4924: I am having a difficult time to understand how an infrared sensor and led work. I have an infrared LED (like the ones you buy anywhere), does it mean that the infrared LED has the frequency os 38khz?
I know that infrared light has a wavelegnth, but does it also have a frequency?

user313: An infrared LED just emits its light (primarily) in the infrared range as described by this Wikipedia article. Any emitted radiated signal (including sound) has both a frequency and a wavelength. The frequency = the velocity of the signal through space divided by its wavelength (F = V / W), or vice-versa: (W = V / F). The natural frequency of light, infrared or visible is far, far higher than 38 KHz; around 4 x 10^14 Hz.
38 KHz is simply a convenient chopping frequency for switching the LED on and off so the sensor can distinguish between infrared in sunlight, for instance, which is relatively constant - from that emitted by the LED. Your circuitry would have to create the 38KHz chopping signal.

4924: <p>I am having a difficult time to understand how an infrared sensor and led work. I have an infrared LED (like the ones you buy anywhere), does it mean that the infrared LED has the frequency os 38khz?</p>

<p>I know that infrared light has a wavelegnth, but does it also have a frequency?</p>
 313: <p>An infrared LED just emits its light (primarily) in the infrared range as described by this <a href="https://en.wikipedia.org/wiki/Infrared" rel="nofollow">Wikipedia article</a>. Any emitted radiated signal (including sound) has both a frequency and a wavelength. The frequency = the velocity of the signal through space divided by its wavelength (F = V / W), or vice-versa: (W = V / F). The natural frequency of light, infrared or visible is far, far higher than 38 KHz; around 4 x 10^14 Hz.</p>

<p>38 KHz is simply a convenient chopping frequency for switching the LED on and off so the sensor can distinguish between infrared in sunlight, for instance, which is relatively constant - from that emitted by the LED. Your circuitry would have to create the 38KHz chopping signal.</p>
