PhET-Simulations-for-Chemistry/C3/Rutherford-Scattering/English-timed

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Time Narration
00:01 Welcome to this tutorial on Rutherford Scattering simulation.
00:06 In this tutorial, we will demonstrate Rutherford Scattering, PhET simulation.
00:13 Here I am using-

Ubuntu Linux OS version 14.04,

00:20 Java version 1.7.0,
00:25 Firefox Web Browser version 53.02.2
00:31 To follow this tutorial, learner should be familiar with topics in high school science.
00:39 Using this simulation, we will learn: about Plum pudding and Rutherford atomic models,
00:48 to visualize the Rutherford gold foil experiment,
00:52 about behavior of alpha particles,
00:56 to identify the factors that affect the deflection of alpha particles.
01:02 Now let us start the demonstration.
01:06 Use the given link to download the simulation.
01:11 I have already downloaded Rutherford Scattering simulation to my Downloads folder.
01:18 To open the simulation, right click on Rutherford Scattering html file.
01:26 Select Open with Firefox Web Browser option.
01:30 File opens in the browser.
01:33 This is the interface of Rutherford Scattering simulation.
01:38 The interface has 2 screens- Rutherford Atom, Plum Pudding Atom.
01:45 Let's begin with Plum Pudding Atom screen.
01:49 J. J. Thomson proposed Plum Pudding atomic model.
01:53 This model was proposed before Rutherford's atomic model.
01:58 Click on Plum Pudding Atom screen to open it.
02:02 Left side of the screen has experimental set up for Plum Pudding atomic model.
02:09 It consists of thin sheet of a metal above the Alpha Particles source.
02:15 Center of the screen has view box.
02:19 It shows a single atom with 3 into 10 to the power of -10 meter atomic scale.
02:26 In the atom, red portion represents the positive charge which is uniformly distributed.
02:33 Small blue spheres represent electrons which are embedded in the atom.
02:39 There is no separation between positive charge and electrons in the atom.
02:44 Screen on the right side shows 2 boxes, Legend and Alpha particle.
02:53 Legend box helps to identify the key components of the atom.
02:58 Alpha Particle box consists of- an Energy slider to change the energy of incoming alpha particles,
03:06 Traces check-box to show an alpha particle's trajectory.
03:11 Check the Traces check-box.
03:14 Bottom of the screen we have, Play/Pause button,
03:19 Step button and Reset button.
03:23 To turn on the Alpha Particles source, click on the blue button.
03:28 Notice that alpha particles beam strikes the thin metal foil.
03:33 Observe the path of alpha particles inside the atom.
03:37 All the alpha particles pass through the atom un-deflected.
03:42 This is because electrons are distributed evenly throughout the atom.
03:47 The magnitude of negative and positive charges inside the atom is equal.
03:53 This gives the most stable electrostatic arrangement.
03:57 Therefore it makes an atom electrically neutral.
04:01 Plum Pudding model was able to explain overall neutrality of the atom.
04:07 Plum Pudding model of an atom failed to explain:

the stability of an atom,

04:15 position of the nucleus in an atom.
04:19 Plum Pudding model could not account for the atomic structure.
04:24 But it provided the base for the development of other atomic structure models.
04:31 Let's move on to Rutherford Atom screen.
04:35 Click on Rutherford Atom screen to open it.
04:39 Rutherford Atom screen helps to visualise the rutherford's gold foil experiment.
04:45 Rutherford Atom screen has same tools as that of Plum Pudding atom screen.
04:51 Additionally, there is an Atom box below Alpha Particle box.
04:56 Atom box consists of Protons and Neutrons sliders to change the composition of the nucleus.
05:04 Here, number of protons and neutrons is equal to that of gold atom.
05:09 At the centre of the screen, you will see a box.
05:13 It represents a zoom in view of different atoms in the gold foil.
05:19 Left side of the screen has 2 model views.
05:23 They are atomic view and nuclear view.
05:27 By default, atomic view is selected.
05:31 Atomic view gives an idea about the behavior of alpha particles as they travel through the atom.
05:38 Click on blue button to turn on the Alpha particles source.
05:43 Notice that alpha particles beam strikes the thin gold foil.
05:48 Check the Traces check-box to see the trajectories of alpha particles.
05:54 Observe the traces of alpha particles as they approach the nuclei of the atoms.
06:00 Now, pause the simulation and click on Step button.
06:06 Here, Most alpha particles are undeflected.
06:11 Some of the alpha particles are slightly deflected.
06:15 A very few alpha particles bounce back, that is, deflected by nearly 180°.
06:22 Let's see the behaviour of alpha particles in nuclear view.
06:27 Click on nuclear view.
06:29 Notice that in zoom in view, atoms are replaced by a single nucleus.
06:35 Now play the simulation.
06:38 Observe the deflections of alpha particles as they approach the nucleus.
06:44 Here n/p ratio for the gold atom is 1.5. Therefore alpha particles show a large deflection.
06:53 Let's study the factors that affect the scattering of alpha particles.
06:59 Drag the Energy slider towards minimum.
07:03 Observe that angles of deflection increases with the decrease in energy.
07:09 Next we will see, how change in composition of nucleus affects scattering of alpha particles.
07:16 Let's start with small nucleus with few number of protons and neutrons.
07:22 Drag the Energy slider back to its default position.
07:27 Then drag the Protons and Neutrons sliders towards 20.
07:32 Size of the nucleus becomes small.
07:35 Observe the angles of deflection of alpha particles.
07:39 Angle of deflection decreases with the decrease in protons and neutrons number.
07:45 Here atom is stable as n /p ratio is 1.
07:50 Observe that alpha particles far from the nucleus have almost no detectable deflection.
07:57 While the alpha particles that are close to the nucleus are deflected.
08:02 As an assignment, try various combinations of protons and neutrons and check the deflections.
08:10 Give an explanation for the change in the behaviour of the alpha particles.
08:16 Let us summarise.
08:19 In this tutorial, we have demonstrated how to use Rutherford Scattering, PhET simulation.
08:28 Using this simulation, we have learnt: about Plum pudding and Rutherford atomic models,
08:37 to visualize the Rutherford gold foil experiment,
08:41 about behavior of alpha particles,
08:45 to identify the factors that affect the deflection of alpha particles.
08:51 The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
09:00 The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates on passing online tests.
09:09 For more details, please write to us.
09:13 Please post your timed queries on this forum.
09:17 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
09:25 Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.

09:38 This is Meenal Ghoderao from IIT Bombay.

Thank you for joining.

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