Neurons process that Many excitatory graded potentials have to happen at once to depolarize the cell body enough to trigger the action potential. When that potential change reaches the trigger zone of the axon, if it is still over threshold, then it will open the voltage gated channels at the trigger zone causing an action potential to be fired. The cell wants to maintain a negative resting membrane potential, so it has a pump that pumps potassium back into the cell and pumps sodium out of the cell at the same time. Reviewer: Action potentials, When efferent (motor) nerves are demyelinated, this can lead to weakness because the brain is expending a lot of energy but is still unable to actually move the affected limbs. These changes cause ion channels to open and the ions to decrease their concentration gradients. with inhibitory input. The overshoot value of the cell potential opens voltage-gated potassium channels, which causes a large potassium efflux, decreasing the cells electropositivity. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. These areas are brimming with voltage-gated ion channels to help push the signal along. Does Counterspell prevent from any further spells being cast on a given turn? Direct link to Ki's post The all-or-none principle, Posted 3 years ago. Neurons have a negative concentration gradient most of the time, meaning there are more positively charged ions outside than inside the cell. into the frequency and duration of a series, which Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. She decides to measure the frequency of website clicks from potential customers. Calculate action potentials (spikes) in the record of a single unit neuronal activity. The information from There are three main events that take place during an action potential: A triggering event occurs that depolarizes the cell body. duration, and direction of graded membrane potentials Go to our nervous system quiz article and ace your next exam. If it were 1-to-1, you'd be absolutely correct in assuming that it doesn't make any sense. This depolarizes the axon hillock, but again, this takes time (I'm purposely repeating that to convey a feeling of this all being a dynamic, moving process, with ions moving through each step). frequency of these bursts. This period overlaps the final 1/3 of repolarization. The myelin is an insulator, so basically nothing can get past the cell membrane at the point. Examples of cells that signal via action potentials are neurons and muscle cells. So, an action potential is generated when a stimulus changes the membrane potential to the values of threshold potential. Therefore, short action potentials provide the nerve cell with the potential for a large dynamic range of signaling. A few sodium ions coming in around the axon hillock is enough to depolarize that membrane enough to start an action potential, but when those ions diffuse passively into the rest of the soma, they have a lot more membrane area to cover, and they don't cause as much depolarization. Histology (6th ed.). And then they'll fire a An action potential is generated in the body of the neuron and propagated through its axon. 2. 2. talk about action potential patterns. Direct link to Geoff Futch's post It has to do with the mec, Posted 5 years ago. This can be anything so long as it repeats. Learn the types of the neurons with the following quiz. The answer lies in how often action potentials are sent - the action potential frequency. Follow Up: struct sockaddr storage initialization by network format-string. ##Consider the following Left column: Canine (HRd model 16 . Calculate the value of t. Give your answer in milliseconds. The top and bottom traces are on the same time scale. excitatory graded potential, also called a depolarization. Direct link to Roger Gerard's post Is the trigger zone menti, Posted 9 years ago. But if there's more If the cell body gets positive enough that it can trigger the voltage-gated sodium channels found in the axon, then the action potential will be sent. Figure 2. Voltage-gated sodium channels have two gates (gate m and gate h), while the potassium channel only has one (gate n). The threshold potential is usually around -50 to -55 mV. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Asking for help, clarification, or responding to other answers. Frequency coding in the nervous system: Supra-threshold stimulus. The charge of the ion does not matter, both positively and negatively charged ions move in the direction that would balance or even out the gradient. During the. and inhibitory inputs can be passed along in a Direct link to Kent Green's post So he specifically mentio, Posted 6 years ago. in the absence of any input. The brutal truth is, just because something seems like a good idea doesnt mean it actually is. Enter the frequency. After the overshoot, the sodium permeability suddenly decreases due to the closing of its channels. and durations. And the same goes for With very strong stimuli, subsequent action potentials occur following the completion of the absolute refractory period of the preceding action potential. Depending on whether the neurotransmitter is excitatory or inhibitory, this will result with different responses. A mass with mass $m$ has a potential energy function $U(x)$ and I'm wondering how you would find the frequency of small oscillations about equilibrium points using Newton's laws. (Convert the is to seconds before calculating the frequency.) During depolarisation voltage-gated sodium ion channels open due to an electrical stimulus. This regular state of a negative concentration gradient is called resting membrane potential. How to skip confirmation with use-package :ensure? more fine-grained fashion. The spike has an amplitude of nearly 100mV and a width at half maximum of about 2.5ms. Postsynaptic conductance changes and the potential changes that accompany them alter the probability that an action potential will be produced in the postsynaptic cell. Gate h (the deactivation gate) is normally open, and swings shut when the cells gets too positive. Are you able to tell me about how an axon may be brought to threshold potential through only the influence of extracellular fluid? Direct link to pesky's post In this sentence "This is, Posted 7 years ago. Learn the structure and the types of the neurons with the following study unit. In this video, I want to Refractory periods also give the neuron some time to replenish the packets of neurotransmitter found at the axon terminal, so that it can keep passing the message along. Using indicator constraint with two variables. What are the normal modes of a velocity-dependent equation of motion? From the ISI you entered, calculate the frequency of action potentials with a prolonged (500 msec) threshold stimulus intensity. excitation goes away, they go back to their Why is there a voltage on my HDMI and coaxial cables? complicated neurons that, in the absence of input, Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Its duration in mammalian A fibres is about 0.4 ms; in frog nerve at 15 o C it is about 2 ms. At What Rate Do Ions Leak Out of a Plasma Membrane Segment That Has No Ion Channels? Upon stimulation, they will either be stimulated, inhibited, or modulated in some way. And inhibitory input will One way to calculate frequency is to divide the number of Impressions by the Reach. Example A: The time for a certain wave to complete a single oscillation is 0.32 seconds. It consists of three phases: depolarization, overshoot, and repolarization. We have a lot of ions flooding into the axon, so the more space they have to travel, the more likely they will be able to keep going in the right direction. If you preorder a special airline meal (e.g. Upon stimulation, they will either be stimulated, inhibited, or modulated in some way. If the action potential was about one msec in duration, the frequency of action potentials could change from once a second to a thousand a second. Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site. During early repolarization, a new action potential is impossible since the sodium channels are inactive and need the resting potential to be in a closed state, from which they can be in an open state once again. 1.4 Components of the Action Potentials Luckily, your body senses that your limbs are in the wrong place and instead of falling to the ground, you just stumble a little. 2023 By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. With the development of electrophysiology and the discovery of electrical activity of neurons, it was discovered that the transmission of signals from neurons to their target tissues is mediated by action potentials. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. The frequency axis (log scale) runs from 300 Hz to 10 kHz and covers 5 octaves. Direct link to Sid Sid's post above there is mention th, Posted 7 years ago. On the other hand, if it inhibits the target cell, it is an inhibitory neurotransmitter. Frequency = 1/ISI. Can Martian regolith be easily melted with microwaves? Im a MBBS and ha. How does (action potential) hyper-polarisation work? If I am right then how is more stimulus causing more frequent action potentials? SNAP amplitudes > 80% of the lower limit of normal (LLN) in two or more nerves. https://www.khanacademy.org/science/biology/membranes-and-transport/active-transport/v/sodium-potassium-pump-video. threshold at the trigger zone, the train of action The second way to speed up a signal in an axon is to insulate it with myelin, a fatty substance. Posted 9 years ago. In addition, after one action potential is generated, neurons become refractory to stimuli for a certain period of time in which they cannot generate another action potential. Use MathJax to format equations. At the same time, the potassium channels open. Can Martian regolith be easily melted with microwaves? Within a row, the electrodes are separated by 250 mm and between rows by 500 mm. Reading time: 11 minutes. is also called a train of action potentials. Philadelphia, PA: Lippincott Williams & Wilkins. Sometimes it is. Your entire brain is made up of this third type of neuron, the interneuron. Frequency = 1/ISI. spontaneously depolarize the membrane to threshold It's like if you touched a warm cup, there's no flinch, but if you touched a boiling pot your flinch "response" would be triggered. This means that as the action potential comes rushing by, it is easier to depolarize the areas that are sheathed, because there are fewer negative ions to counteract. At the neuromuscular junction, synaptic action increases the probability that an action potential will occur in the postsynaptic muscle cell; indeed, the large amplitude of the EPP ensures that an action potential always is . Do roots of these polynomials approach the negative of the Euler-Mascheroni constant? How greater magnitude implies greater frequency of action potential? Myelin increases the propagation speed because it increases the thickness of the fiber. Why do many companies reject expired SSL certificates as bugs in bug bounties? The spatial orientation of the 16 electrodes in this figure is such that the top two rows are physically on the left of the bottom two rows. Guillain-Barre syndrome is the destruction of Schwann cells (in the peripheral nervous system), while MS is caused by a loss of oligodendrocytes (in the brain and spinal column). Patestas, M. A., Gartner, L. P. (2006). There is actually a video here on KA that addresses this: How does the calcium play a role in all of this? Some neurons fire Ion concentrations and ion permeabilities set an equilibrium potential, but, it takes time for the potential to actually reach that equilibrium, and both the present voltage and equilibrium potential can be different in different parts of the cell: this leads to current flow, which takes time. An action potential propagates along the cell membrane of an axon until it reaches the terminal button. When the myelin coating of nerves degenerates, the signals are either diminished or completely destroyed. We say these channels are voltage-gated because they are open and closed depends on the voltage difference across the cell membrane. Ions are flowing in and out of the neuron constantly as the ions try to equalize their concentrations. spike to represent one action potential. We then end up with thin layers of negative ions inside of the cell membrane and positive ions outside the cell membrane. So he specifically mentioned the motor neurons as the ones that are silent until they have sufficient excitation; and then they fire frequently until the excitation goes away. Sensory information is frequency-modulated in that the strength of response is directly related to the frequency of APs elicited in the sensory nerve. Greater the magnitude of receptor potential, greater is the rate of discharge of action potentials in the nerve fibre.1 Now consider a case where stimulus ( strength ) is large , so there is more accumulation of positive charges near the spike generator region, this would then form action potential , this action potential should then travel in both directions just like at initial segment . In the central nervous system, oligodendrocytes are responsible for insulation. Author: Direct link to Julie Rose's post An example of inhibitory , Posted 6 years ago. It can cause changes Relative refractoriness is the period when the generation of a new action potential is possible, but only upon a suprathreshold stimulus. This calculator provides BMI and the corresponding BMI-for-age percentile on a CDC BMI-for-age growth chart. 3. The resting potential is -60 mV. neurons, excitatory input can cause the little bursts The Children's BMI Tool for Schools School staff, child care leaders, and other professionals can use this spreadsheet to compute BMI for as many as 2,000 children. 2. in the dendrites and the soma, so that a small excitatory Repolarization always leads first to hyperpolarization, a state in which the membrane potential is more negative than the default membrane potential. Here, a cycle refers to the full duration of the action potential (absolute refractory period + relative refractory period). Action potentials (those electrical impulses that send signals around your body) are nothing more than a temporary shift (from negative to positive) in the neurons membrane potential caused by ions suddenly flowing in and out of the neuron. All rights reserved. How to notate a grace note at the start of a bar with lilypond? Concentration gradients are key behind how action potentials work. With these types of In this example, the temperature is the stimulus. Absolute refractory periods help direct the action potential down the axon, because only channels further downstream can open and let in depolarizing ions. The change in membrane potential isn't just because ions flow: it's because permeabilities change, briefly creating a new equilibrium potential. over threshold right here, then we see a little train In practice, you should check your intermediate . If the nerves are afferent (sensory) fibers, the destruction of myelin leads to numbness or tingling, because sensations arent traveling the way they should. Any help would be appreciated, It's always possible to expand the potential in Taylor series around any local minima (in this example $U(x) $ has local minima at $x_0$ , thus $U'(x_0)=0 $ ), $$ U(x) \approx U(x_0)+\frac{1}{2}U''(x_0)(x-x_0)^2 $$, Setting $ U(x_0)=0 $ and $ x_0=0$ (for simplicity, the result don't depend on this) and equating to familiar simple harmonic oscillator potential we get -, $$ \frac{1}{2}kx^2=\frac{1}{2}m\omega^2x^2=\frac{1}{2}U''(x_0)x^2 $$, $$ \omega =\sqrt{\frac{k}{m}}=\sqrt{\frac{U''(x_0)}{m}} $$. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Let's explore how the graph of stopping potential vs frequency can be used to calculate the Planck's constant experimentally! The information is sent via electro-chemical signals known as action potentials that travel down the length of the neuron. Let's explore how the graph of stopping potential vs frequency can be used to calculate the Planck's constant experimentally! how is the "spontaneous action potential" affected by the resting potential? Direct link to Bailey Lee's post A diameter is a line that, Posted 4 years ago. Connect and share knowledge within a single location that is structured and easy to search. Diagram of large-diameter axon vs small diameter axon. 17-15 ), even at rates as low as 0.5 Hz, and they may not be apparent after the first 3 or 4 stimuli. --> Would this mean that it then takes, @Pugl Both are possible, on different time scales. these neurons that doesn't fire any action potentials at rest. This is done by comparing the electrical potentials detected by each of the electrodes. Millikan, Einstein, and Max Planck, all won a Nobel prize for their contribution to photoelectric effect and giving birth to the quantum nature of light! Direct link to Gyroscope99's post Is ion exchange occurring, Posted 7 years ago. Absolute refractoriness ends when enough sodium channels recover from their inactive state. Direct link to christalvorbach's post How does calcium decrease, Posted a year ago. however, are consistently the same size and duration 1 2 k x 2 = 1 2 m 2 x 2 = 1 2 U ( x 0) x 2. That will slow down their Philadelphia, PA: Lippincott Williams & Wilkins. From the ISI you entered, calculate the frequency of action potentials with a prolonged (500 msec) threshold stimulus intensity. I also know from Newton's 2nd Law that In humans, synapses are chemical, meaning that the nerve impulse is transmitted from the axon ending to the target tissue by the chemical substances called neurotransmitters (ligands). vegan) just to try it, does this inconvenience the caterers and staff? The speed of propagation largely depends on the thickness of the axon and whether its myelinated or not. We have emphasized that once the depolarization caused by the stimulus is above threshold, the resulting neuronal action potential is a complete action potential (i.e., it is all-or-nothing). Hi, which one of these do neurons of the digestive tract identify with? A question about derivation of the potential energy around the stable equilibrium point. The frequency is the reciprocal of the interval and is usually expressed in hertz (Hz), which is events (action potentials) per second. The most important property of the Hodgkin-Huxley model is its ability to generate action potentials. Brain cells called neurons send information and instructions throughout the brain and body. Graded potentials are small changes in membrane potential that are either excitatory (depolarize the membrane) or inhibitory (hyperpolarize the membrane). Since the neuron is at a negative membrane potential, its got a lot of agitated negative ions that dont have a positive ion nearby to balance them out. If the stimulus strength is increased, the size of the action potential does not get larger (see, Given that the frequency of action potentials is determined by the strength of the stimulus, a plausible question to ask is what is the frequency of action potentials in neurons? But with these types If you're seeing this message, it means we're having trouble loading external resources on our website. Conduction of action potentials requires voltage-gated sodium channels. From Einstein's photoelectric equation, this graph is a straight line with the slope being a universal constant. Learn more about Stack Overflow the company, and our products. Thanks for contributing an answer to Biology Stack Exchange! Direct link to matthewjrodden1's post Hey great stuff, Use MathJax to format equations. Direct link to Danielle Jettoo's post Im wondering how these gr, Posted 6 years ago. The m gate is closed, and does not let sodium ions through. Subthreshold stimuli cannot cause an action potential. Spontaneous action potential occurs when the resting potential is depolarized above the threshold action potential. = k m = U ( x 0) m. Share. Making statements based on opinion; back them up with references or personal experience. In an effort to disprove Einstein, Robert Millikan . Are there tables of wastage rates for different fruit and veg? The same would also be true if there were more of one type of charged ion inside the cell than outside. (1/160) x 1000 = 6.25 ms \end{align}, but I'm not sure where to continue this approach either because there is an expression in terms of displacement on the LHS, and an expression in terms of time on the RHS. I dont know but you will get cramps from swimming if you dont eat enough potassium. to happen more frequently. Direct link to Fraley Dominic's post I dont know but you will , Posted 2 years ago. A Textbook of Neuroanatomy. Is it a sodium leak channel? To learn more, see our tips on writing great answers. Help understanding what the Hamiltonian signifies for the action compared with the Euler-Lagrange equations for the Lagrangian? This continues down the axon and creates the action potential. And we'll look at the temporal There is a maximum frequency at which a single neuron can send action potentials, and this is determined by its refractory periods. Larger diameter axons have a higher conduction velocity, which means they are able to send signals faster. A comprehensive guide on finding co-founders, including what to look for in them, 14 places to find them, how to evaluate them and how to split equity. 3. . neurons, that information can't be passed along. Calculation of the oscillation frequency of a rotating system that performs small oscillations. As the initial axon segment recovers from post-action potential hyperpolarization and sodium channels leave their inactivated state, current from the receptor potential is flowing in, depolarizing the cell to threshold and causing another spike. toward the terminal where voltage gated Ca2+ channels will open and let Ca2+ inside where the synaptic vesicles will fuse with the presynaptic membrane and let out their contents in the synapse (typically neurotransmitters). Relative refractory periods can help us figure how intense a stimulus is - cells in your retina will send signals faster in bright light than in dim light, because the trigger is stronger. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. An action potential is a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane with a characteristic pattern. However, they have a few extra features which allow them to be fantastic at transferring action potentials: Illustration of the neuron with the dendrites, myelin sheath, axon, and axon terminus labelled. This means that any subthreshold stimulus will cause nothing, while threshold and suprathreshold stimuli produce a full response of the excitable cell. Not all stimuli can cause an action potential. In neurons, it is caused by the inactivation of the Na + channels that originally opened to depolarize the membrane. 4. Again, the situation is analogous to a burning fuse. An action potential is defined as a sudden, fast, transitory, and propagating change of the resting membrane potential. However, the sodium/potassium pump removes 3 sodium ions from the cell while only allowing 2 potassium ions in. This is the period after the absolute refractory period, when the h gates are open again. Is an action potential different depending on whether its caused by threshold or suprathreshold potential? The neuron cell membrane is super permeable to potassium ions, and so lots of potassium leaks out of the neuron through potassium leakage channels (holes in the cell wall). The all-or-none principle is for the "response" to a stimulus. During trains of repetitive nerve stimulation, consecutive repetitive CMAPs are smaller than the preceding ones (see Fig. Higher frequencies are also observed, but the maximum frequency is ultimately limited by the, Because the absolute refractory period can last between 1-2 ms, the maximum frequency response is 500-1000 s. A cycle here refers to the duration of the absolute refractory period, which when the strength of the stimulus is very high, is also the duration of an action potential. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. duration of depolarization over threshold is converted I hope this helps. . And then when that For example, a cell may fire at 1 Hz, then fire at 4 Hz, then fire at 16 Hz, then fire at 64 Hz. \mathbf{F} &= m \mathbf{\ddot{x}} \\ This means that the action potential doesnt move but rather causes a new action potential of the adjacent segment of the neuronal membrane. Follow these steps to calculate frequency: 1. Direct link to Kiet Truong's post So in a typical neuron, P, Posted 4 years ago. sufficient excitatory input to depolarize the trigger zone To log in and use all the features of Khan Academy, please enable JavaScript in your browser. This is because there is less resistance facing the ion flow. Adequate stimulus must have a sufficient electrocal value which will reduce the negativity of the nerve cell to the threshold of the action potential. It can only go from no Use this calculator for children and teens, aged 2 through 19 years old. In an action potential graph, why does a refractory period start immediately after the triggering of an action potential and not at the start of the repolarization phase? Item Value: Notes: Quantity: 5: Number of Spots: Rate: $ 500.00: Cost Per Spot: Media . inhibitory inputs. Linear regulator thermal information missing in datasheet. The stimulation strength can be different, only when the stimulus exceeds the threshold potential, the nerve will give a complete response; otherwise, there is no response. Because of this, an action potential always propagates from the neuronal body, through the axon to the target tissue. Clinically Oriented Anatomy (7th ed.). But your nerves dont just say hand, move. Instead your nerves send lots of electrical impulses (called action potentials) to different muscles in your hand, allowing you to move your hand with extreme precision. inhibitory input to these types of the man standing next to einstein is robert milliken he's pretty famous for his discovery of the charge of the electron but he also has a very nice story uh in photoelectric effect turns out when he looked at the einstein's photoelectric equation he found something so weird in it that he was convinced it had to be wrong he was so convinced that he dedicated the next 10 years of life coming up with experiments to prove that this equation had to be wrong and so in this video let's explore what is so weird in this equation that convinced robert millican that it had to be wrong and we'll also see eventually what ended up happening okay so to begin with this equation doesn't seem very weird to me in fact it makes a lot of sense now when an electron absorbs a photon it uses a part of its energy to escape from the metal the work function and the rest of the energy comes out as its kinetic energy so makes a lot of sense so what was so weird about it to see what's so weird let's simplify a little bit and try to find the connection between frequency of the light and the stopping potential we'll simplify it makes sense so if we simplify how do we calculate the energy of the photon in terms of frequency well it becomes h times f where f is the frequency of the incident light and that equals work function um how do we simplify work function well work function is the minimum energy needed so i could write that as h times the minimum frequency needed for photoelectric effect plus how what can we write kinetic energy as we can write that in terms of stopping voltage we've seen before in our previous videos that experimentally kinetic maximum kinetic energy with the electrons come out is basically the stopping voltage in electron volt so we can write this to be e times v stop and if you're not familiar about how you know why this is equal to this then it'll be a great idea to go back and watch our videos on this we'll discuss it in great detail but basically if electrons are coming out with more kinetic energy it will take more voltage to stop them so they have a very direct correlation all right again do i do you see anything weird in this equation i don't but let's isolate stopping voltage and try to write the equation rearrange this equation so to isolate stopping voltage what i'll do is divide the whole equation by e so i'll divide by e and now let's write what vs equals vs equals let's see v cancels out we get equals hf divided by e i'm just rearranging this hf divided by e minus minus h f naught divided by e does this equation seem weird well let's see in this entire equation stopping voltage and the frequency of the light are the only variables right this is the planck's constant which is a constant electric charge is a const charge and the electron is a constant threshold frequency is also a constant for a given material so for a given material we only have two variables and since there is a linear relationship between them both have the power one that means if i were to draw a graph of say stopping voltage versus frequency i will get a straight line now again that shouldn't be too weird because as frequency increases stopping potential will increase that makes sense right if you increase the frequency the energy of the photon increases and therefore the electrons will come out with more energy and therefore the stopping voltage required is more so this makes sense but let's concentrate on the slope of that straight line that's where all the weird stuff lies so to concentrate on the slope what we'll do is let's write this as a standard equation for a straight line in the form of y equals mx plus c so over here if the stopping voltage is plotted on the y axis this will become y and then the frequency will be plotted on the x axis so this will become x and whatever comes along with x is the slope and so h divided by e is going to be our slope minus this whole thing becomes a constant for a given material this number stays the same and now look at the slope the slope happens to be h divided by e which is a universal constant this means according to einstein's equation if you plot a graph of if you conduct photoelectric effect and plot a graph of stopping voltage versus frequency for any material in this universe einstein's equation says the slope of that graph has to be the same and millikan is saying why would that be true why should that be true and that's what he finds so weird in fact let us draw this graph it will make more sense so let's take a couple of minutes to draw this graph so on the y-axis we are plotting the stopping voltage and on the x-axis we are plotting the frequency of the light so here's the frequency of the light okay let's try to plot this graph so one of the best ways to plot is plot one point is especially a straight line is you put f equal to zero and see what happens put vs equal to zero and see what happens and then plot it so i put f equal to 0 this whole thing becomes 0 and i get vs equal to minus h f naught by e so that means when f is equal to 0 vs equals somewhere over here this will be minus h of naught by e and now let's put vs equal to 0 and see what happens when i put vs equal to 0 you can see these two will be equal to each other that means f will become equal to f naught so that means when when vs equal to 0 f will equal f naught i don't know where that f naught is maybe somewhere over here and so i know now the graph is going to be a straight line like this so i can draw that straight line so my graph is going to be a straight line that looks like this let me draw a little thinner line all right there we go and so what is this graph saying the graph is saying that as you increase the frequency of the light the stopping voltage increases which makes sense if you decrease the frequency the stopping voltage decreases and in fact if you go below the stopping voltage of course the graph is now saying that the sorry below the threshold frequency the graph is saying that the stopping voltage will become negative but it can't right below the threshold frequency this equation doesn't work you get shopping voltage to be zero so of course the way to read this graph is you'll get no photoelectric effect till here and then you will get photoelectric effects dropping voltage so this is like you can imagine this to be hypothetical but the focus over here is on the slope of this graph the slope of this graph is a universal constant h over e which means if i were to plot this graph for some other material which has say a higher threshold frequency a different threshold frequency somewhere over here then for that material the graph would have the same slope and if i were to plot it for some another let's take another material which has let's say little lower threshold frequency again the graph should have the same slope and this is what millikan thought how why should this be the case he thought that different materials should have different slopes why should they have the same slope and therefore he decided to actually experimentally you know actually conduct experiments on various photoelectric materials that he would get his hands on he devised techniques to make them make the surfaces as clean as possible to get rid of all the impurities and after 10 long years of research you know what he found he found that indeed all the materials that he tested they got the same slope so what ended up happening is he wanted to disprove einstein but he ended up experimenting proving that the slope was same and as a result he actually experimentally proved that einstein's equation was right he was disappointed of course but now beyond a doubt he had proved einstein was right and as a result his theory got strengthened and einstein won a nobel prize actually for the discovery you know for this for his contribution to photoelectric effect and this had another significance you see the way max planck came up with the value of his constant the planck's constant was he looked at certain experimental data he came up with a mathematical expression to fit that data and that expression which is called planck's law had this constant in it and he adjusted the value of this constant to actually fit that experimental data that's how we came up with this value but now we could conduct a completely different experiment and calculate the value of h experimentally you can calculate the slope here experimentally and then you can we know the value of e you can calculate the value of h and people did that and when they did they found that the value experimentally conducted over here calculated over here was in agreement with what max planck had originally given and as a result even his theory got supported and he too won their nobel prize and of course robert milliken also won the nobel prize for his contributions for this experimentally proving the photo electric effect all in all it's a great story for everyone but turns out that millikan was still not convinced even after experimentally proving it he still remained a skeptic just goes to show how revolutionary and how difficult it was to adopt this idea of quantum nature of light back then.
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