 Let's solve a couple of questions on figuring out frequency and amplitude from from graphs. So for the first one, we have a transverse wave on a string which travels at 20 meters per second. A graph of the height of the wave along the x direction at a certain moment is shown, not below, but to the side. Now, what is the frequency of the wave along the string? Okay, as always pause the video and try this one on your own first. All right, hopefully you gave this a short. Now we need to figure out frequency, right? This is F, that is what we need to figure out. Let's try to think back what was frequency. Well, frequency really was the number of vibrations per second. It was the number of vibrations or oscillations, the number of vibrations or oscillations per second. That was frequency and the relation to figure out this was 1 by T. Now, in this graph, we know the height of all the particles in a snapshot of time. So the entire string is oscillating and this is a snapshot in time when we see the displacement of each and every each and every point on the string. The good thing is that we know the speed and we can actually try and figure out the wavelength from this graph, right? Wavelength was the distance between two consecutive maximas or two consecutive minimas. So for this wave, the wavelength really is 2 meters. We can see it is 2 meters. And from the wave equation, on the wave equation, we know that the wave speed V that is equal to lambda into F. This is lambda into F. We already know what the speed is that is 20 and we just figured out the wavelength. So we can work out frequency. Frequency then, frequency then is V divided by lambda and in this case, it will be 20. This will be 20 divided by 2. So this comes out to be equal to 10 hertz. Okay, let's look at one more question. Here, the vertical position of a certain point on a string over time is shown. What is the amplitude of the wave? Okay, we need to choose one answer and we have a displacement time graph. Again, pause the video, first try this one on your own. Okay, so now here we can ask ourselves what is amplitude? Amplitude, this was the distance between the midline or the equilibrium line. We can write the midline and the maximum point of displacement or we can write and the crest or the trough. So this was amplitude, distance between the midline and the crest or trough. Maximum positive displacement or maximum negative displacement from the equilibrium line that was amplitude. In the graph, we know, we can see that this distance right here, the distance between the crest and the trough. That is really, it's starting from 2 and going till minus 4. So this distance really is 6 meters because covering 1, 2, 3, 4, 5, 6 meters. And we know that the amplitude is really the half of this value. It's really the half of the distance between the crest and the trough. So 6 by 2, this is 3 meters and that's the amplitude. Amplitude is 3 meters over here. 6 meters is the distance between the crest and the trough. Amplitude is always the half of that. 3 seconds, this is the wrong unit and minus 3 meters is again wrong because amplitude is always taken as positive as it is the distance between the midline and the crest. When I say maximum positive displacement or maximum negative displacement, we are really taking the magnitude of that at the end of the day. So we are really considering only the distance. And if we do try to draw the midline for this wave, that will be somewhere, somewhere, somewhere here. That could be the midline, the midline of the wave. Alright, you can try more questions from this exercise in the lesson and if you're watching on YouTube, do check out the exercise link which is added in the description.