Well, we all know a thing or two about quantum physics. Some of which i have discussed earlier in my blog. But where did all these originate from?
As all great ideas start. This idea too started with a light bulb.
In the early 1890s German physicist Max Planck was given a task from the German government to make a light bulb with greater efficiency. The main dilemma faced by Planck was to create a light bulb which emitted maximum radiation in the visible spectrum. His first task was to predict how much light a hot filament gives off. He knew that light consisted of electromagnetic waves that had different frequencies (visible being one of them).
He tried to work out how much light of each frequency (or color) a hot object emits. His initial predictions contradicted the observations of the electromagnetic theory. Hence, in an act of despair he threw out all the known theories out of the window and started working backwards from the experimental measurements. The data he then received pointed him towards a new rule of physics.
What he deduced from his new theory that "light waves carry energy only in packets". With high frequency light consisting of large packets and low energy lights consisting of low energy packets. This idea itself at that time sounded too vague and illogical. But Einstein soon related it to a much more familiar problem.
Sharing
Lets say we are in a party. There are many kids here, and we just have one cake. Now lets consider this cake as energy we have. So, if we give the entire cake to one kid, what we get is a very happy and excited kid, lets say this happy and excited kid is a high frequency photon. Now, if we divide this cake into two kids the level of excitement would decrease, hence the energy of the photon would decrease. If we further divide it into infinite kids, what we get is a mob of unhappy kids, hence we receive lower frequency (or lower energy) photons.
But if this were completely true, we would have lost all heat from the universe (because as I stated in my earlier post, every body has its own radiation). But this does not happen. It turns out that these kids or photons are extremely choosey in their share of the cake. Some want 3/4 of the cake. Not much, not less. Similarly, in case of photons, they too are very choosey in their share of energy. Hence as plank guessed, the photons can only carry energy in very discrete bundles. Hence high frequency (or high energy) photons can only carry high energies. Hence when the body runs low on energy, it becomes incapable of fulfilling the needs to radiate high frequency photons. Hence, it ends up radiating lower frequency photons.
Hence, a colder body radiates photons of lower frequency and hotter body radiates photons with higher frequencies. The common average energy that the packets carry out of the body (or radiate out of the body) is in fact what we know as Temperature. So at higher temperature (meaning higher average energy) the photons radiated are of higher frequency. Hence when you heat a body, it first glows in infrared spectrum, then glows red, then yellow, then white, more hotter towards blue, violet, and then ultraviolet, so on and so forth.
Hence by planks quantum theory we can deduce that, a light bulb filament should be heated to temperatures from 2700~3200 kelvins to ensure most of the energy is emitted as visible waves. Any much hotter and we would start tanning ourselves from the UV radiations emitted.
As all great ideas start. This idea too started with a light bulb.
In the early 1890s German physicist Max Planck was given a task from the German government to make a light bulb with greater efficiency. The main dilemma faced by Planck was to create a light bulb which emitted maximum radiation in the visible spectrum. His first task was to predict how much light a hot filament gives off. He knew that light consisted of electromagnetic waves that had different frequencies (visible being one of them).He tried to work out how much light of each frequency (or color) a hot object emits. His initial predictions contradicted the observations of the electromagnetic theory. Hence, in an act of despair he threw out all the known theories out of the window and started working backwards from the experimental measurements. The data he then received pointed him towards a new rule of physics.
What he deduced from his new theory that "light waves carry energy only in packets". With high frequency light consisting of large packets and low energy lights consisting of low energy packets. This idea itself at that time sounded too vague and illogical. But Einstein soon related it to a much more familiar problem.
Sharing
Lets say we are in a party. There are many kids here, and we just have one cake. Now lets consider this cake as energy we have. So, if we give the entire cake to one kid, what we get is a very happy and excited kid, lets say this happy and excited kid is a high frequency photon. Now, if we divide this cake into two kids the level of excitement would decrease, hence the energy of the photon would decrease. If we further divide it into infinite kids, what we get is a mob of unhappy kids, hence we receive lower frequency (or lower energy) photons. But if this were completely true, we would have lost all heat from the universe (because as I stated in my earlier post, every body has its own radiation). But this does not happen. It turns out that these kids or photons are extremely choosey in their share of the cake. Some want 3/4 of the cake. Not much, not less. Similarly, in case of photons, they too are very choosey in their share of energy. Hence as plank guessed, the photons can only carry energy in very discrete bundles. Hence high frequency (or high energy) photons can only carry high energies. Hence when the body runs low on energy, it becomes incapable of fulfilling the needs to radiate high frequency photons. Hence, it ends up radiating lower frequency photons.
Hence, a colder body radiates photons of lower frequency and hotter body radiates photons with higher frequencies. The common average energy that the packets carry out of the body (or radiate out of the body) is in fact what we know as Temperature. So at higher temperature (meaning higher average energy) the photons radiated are of higher frequency. Hence when you heat a body, it first glows in infrared spectrum, then glows red, then yellow, then white, more hotter towards blue, violet, and then ultraviolet, so on and so forth.Hence by planks quantum theory we can deduce that, a light bulb filament should be heated to temperatures from 2700~3200 kelvins to ensure most of the energy is emitted as visible waves. Any much hotter and we would start tanning ourselves from the UV radiations emitted.
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