# Question about frequency of light

• 1v1Dota2RightMeow
In summary, you can flicker an LED on and off at a rate on the order of hundreds of kHz, even though the light is generated through the excitation and relaxation of electrons between electronic states.
1v1Dota2RightMeow
I flicker an LED on and off at a rate on the order of hundreds of kHz. The light, even though it is sent in pulses, still has its own frequency, correct? The frequency at which I turn the light on and off is not related to the frequency of the photons. Is this correct?

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1v1Dota2RightMeow said:
I flicker a lightbulb on and off at a rate on the order of hundreds of kHz
You cannot do that. The response time of a light bulb is much longer than that.

For an incandescent bulb, you will get a spectrum based on the temprature of the filament.

Orodruin said:
You cannot do that. The response time of a light bulb is much longer than that.

For an incandescent bulb, you will get a spectrum based on the temprature of the filament.

*For an LED, which responds to current fluctuations on the order of microseconds

The LED itself generates light through the excitation and relaxation of electrons between electronic states. In other words, when you apply a voltage and send a current through an LED, you are exciting electrons from lower states of energy into higher states. When they fall to a lower energy state, they release that energy as a photon of light whose energy is the same as the difference in the energy states. So the rate at which you switch the LED on and off has little to do with how the light is generated.

1v1Dota2RightMeow said:
I flicker an LED on and off at a rate on the order of hundreds of kHz. The light, even though it is sent in pulses, still has its own frequency, correct? The frequency at which I turn the light on and off is not related to the frequency of the photons. Is this correct?
That is correct as long as the frequency of the light is large compared with the frequency with which you flash the light, which is the case here - the frequency of visible light is measured in the hundreds of terahertz and you are cycling the light at hundreds of kilohertz.

You might try imagining the same experiment with sound waves. Sound waves typically have a frequency of hundreds of hz, so your experiment is analogous to switching a sound generator on and off every few months.

(As an aside, there aren't any photons involved here. This is a purely classical thought experiment, and the light is best thought of as electromagnetic waves. Photons only come into the picture when there are significant quantum mechanical effects, and that's not the case here.).

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Orodruin

## What is the frequency of light?

The frequency of light refers to the number of times a wave of light oscillates per second. It is measured in Hertz (Hz) and can range from millions to trillions of cycles per second.

## How is the frequency of light related to its color?

The frequency of light determines its color. Higher frequencies correspond to shorter wavelengths and are associated with colors such as violet and blue. Lower frequencies have longer wavelengths and are associated with colors such as red and orange.

## What is the electromagnetic spectrum?

The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation, including light. It includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

## Can the frequency of light be changed?

Yes, the frequency of light can be changed by altering the energy of the light source. For example, heating an object can increase the energy of its atoms, causing them to emit higher frequency light. Passing light through a prism can also separate it into different frequencies.

## What are some applications of frequency of light?

The frequency of light has many applications in various fields. In medicine, it is used in imaging techniques such as X-rays and MRI scans. In telecommunications, it is used for transmitting data through fiber optic cables. It is also essential in astronomy for studying the properties of celestial objects.

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