Humanity has relied on light to live and survive since time immemorial, and our ancestors have likened it to a blessing, that is until they domesticated it upon discovering how to make fire and inventing the light bulb.
But while we now freely harness light in our daily lives, many do not fully understand how light is produced from the bulbs in our many devices and appliances. If we take a traditional incandescent light bulb, for example, we know that it produces light upon receiving current. This current heats the tungsten filament in the middle to 2500℃, generating countless photons that light up a room.
This begs the question: if heated objects emit light, why do warm-blooded mammals like humans do not produce light as light bulbs do? The fact that our body temperature is nowhere near the thousands is only part of the reasoning. The full explanation is that we do emit light, but it is so insignificant and virtually “invisible” to our eyes due to the paltry amount of heat we produce. However, the magnitude of energy is not solely to blame as CFL tubes and modern LED bulbs do not get nearly as hot as incandescent bulbs, yet they are just as bright.
A Closer Look at Photons
As you may recall from your IP physics tuition in Singapore, light is generated by the acceleration of photons or charged particles, making it an electromagnetic wave by the law of electromagnetism. Photons are defined as excitations of the electromagnetic field. According to Maxwell’s laws, exciting this electric field, which in turn excites the magnetic field and then re-excites the electric field in a continuous loop, first requires exciting the electrons.
These electrons are found at different energy levels within an atom. When electrons get excited, such as in the case of an incandescent bulb turning on, those found in the atoms of the tungsten filament get elevated to higher energy levels. Nature seeks stability, however, which is why electrons are averse to climbing to much higher levels and will eventually go back to their original level or sometimes lower. This downward leap results in a by-product of the atom releasing or emitting a photon. When we multiply this reaction by the billions, it becomes clear how the heated tungsten can unleash an innumerable amount of photos.
The Energy of a Photon
The light generated by these reactions can either be invisible or visible to the naked eye depending on two factors: the energy of the photon and the frequency of the electromagnetic wave. As a refresher, the electromagnetic spectrum consists of seven categories, with only one being detectable to the human eye. Moreover, a photon’s energy or the frequency of an electromagnetic wave directly corresponds to how far an electron ‘jumps’ or the distance it travels.
Returning to the tungsten filament example, the electrons that are moved to a higher energy level and back down translate to a frequency within the visible spectrum, meaning the photons they produce are visible. However, leaps or movements to a space beyond this range, no matter how big or small, will generate invisible photons. This is why humans and warm-blooded animals produce light undetectable to the eye, only by devices designed to detect low-frequency infrared waves.
Understanding the Significance of Elevation
All in all, it makes no difference in how electrons get excited—be it via electricity or heat—since the magnitude of their elevation is the only thing that matters. This realisation is why we no longer associate more heat, which equates to more light.
Although this notion still has some truth to it, as seen in stars, it is highly inefficient, so incandescent bulbs are known to waste significant amounts of heat energy, unlike CFLs, which simply pass electricity through argon and mercury-filled tubes to excite electrons.
Conclusion
So, we have established that light, or more specifically photons, is created when an electron goes from a higher energy level to a lower level. However, that does not mean countless photons just sit idly inside an atom, ready to go at the electrons’ command. As explained, an electron will go back to a lower energy level from a higher one after getting excited to maintain stability. This transition loses the energy that caused the electron to climb higher in the first place, causing the instantaneous creation of a photon. Such a phenomenon occurs since the laws of our universe dictate that organised energy cannot be squandered, hence why photons can just pop into existence in this process.
Beyond how light works, most people only have a surface-level understanding of the many things they interact with daily. If you want to change that, consider signing up for our classes at Tuition Physics! With the help of our comprehensive and engaging curriculum and highly committed physics tutors in Singapore, reaching your full potential in physics is easier than ever. Feel free to contact us today to learn more about our syllabi, class schedule, and other details about our renowned tuition programmes!
