Using virtual PHET media in the physics lessons for explaining atom structure

. The analysis of experiments carried out on revealing expediency using virtual laboratory works on atomic and nuclear physics in PHET medium has been presented. The main possibilities and advantages this medium in comparison of traditional lessons are listed. It has been shown that using such medium allows improve essentially knowledge and perception of the real picture of atomic structure by pupils.


Introduction
The modern method of school education differs essentially from traditional one on many criteria, in particularly, possibility giving pupils the more information in period of one lesson.Today pupils must not only master giving by teacher, but also learn to handle information, construct conclusions and make decisions based obtained information comparing it with other sources and living experiences.Continuous self-learning allows pupil keep up with the times and be carrier of such valuable resources in modern society both knowledge and skills, acquire new information, transform it and use one for solution investigating problem.
Therefore, there are new requirements to the modern lesson: formation aims and tasks by same pupils, independent planning by ones methods for reaching aims, realize independent correction of difficulties.
Representation of wide information is actual task of collection of virtual educational objects in the virtual educational medium because of the information represented even by modern lesson issues is not enough for studying.This medium allows to absolute each pupil both by under the guidance of teacher and as independent observe phenomena, find the different sides of studying objects, realize the essence of studying law.
Pupils in period of lesson obtain information not only from the teacher and textbook, but also by making laboratory works, that is both on lessons and also in the home conditions.The obligatory part of the modern lesson process is the practicum realizing in the laboratory conditions, the main tasks that are:  formation practical knowledge and skills for working with the different equipment;  obtain and analyze the experimental data;  skills for works planning;  analyze the results and comparison them with known well data.
In duration of lesson on physics subject we must take into account that realization of information technologies to the educational process will be justified if it adds effectively the having educational technologies or has additional advantages in comparison of the traditional educational forms.
For example, using virtual laboratory works and laboratory experiments in teaching physics allows us make laboratory works more interesting and experiments more brighter than traditional ones, while increasing interest of pupils to the studying subject.The complex of such works usually include:  modelling processes and phenomena;  data sources;  instruments for interpretation of output results;  Internet.The physical experiments carried out at school in duration of laboratory works contribute for creation on pupils the real picture on the phenomena and processes.Pupils in duration of the independent performing experiments and experiences know the physical laws, study of working rules with laboratory equipment.Conducting this kind of experiments contribute for construction of investigating skills.However, at present not always is possible involve everyone in the work.One of the first reasons is absence of the required quantity of equipment.The school equipment can be equipped not always with the necessary devices, reagents and laboratory works, demonstrations conducting manuals.The second reason is that equipment can be fail or become obsolete.Besides, in the physical subject there are many lessons implementation of which should be by strict adherence of the technical and fire safety rules.It should be noted, there are works, which are impossible to complete in a school setting, for example, phenomena cannot be observed in the real conditions.Optics, quantum and nuclear physics require the laboratory equipment, which are absence not only in schools, but also in many higher educational institutes.
It is unlikely that a pupil can imagine what is the ampermeter based only on the teacher explains.Teacher in ones turn can use several methods for explaining the new device: by picture (poster, picture from the projector); by demonstration of real ampermeter and its working principles.
Assimilation by pupils of educational material, formation of scientific presentations on the physical processes and phenomena, providing strong and deep knowledge are due to observance on of the main teaching principle, namely, visibility principle, which we must take into account in the present days too.

Review of the latest investigations
The different methods and devices for realization of visibility principle at school are used.In particularly, for that contribute the real laboratory works which to frontal, individual and sectional ones are divided.Today taking into account technologies development and requirement for independent obtain knowledge by pupils we must use the virtual laboratory works (VLW) which have the same functions as in the real ones.Producing the investigating skills, it is important to understand that this is impossible, if we use only classic teaching technologies.Namely in that its advantages: computer models give possibility for taking into account the individual character of pupils, that is each pupil can chose the individual temp for study of the material, consolidate and evaluate results.
The main advantage of VLW is its safety.Unlike from execution of real laboratory works in using VLW is possible observe wrong progress, consequences and others.Besides, it is important that the program is not "paused" when it executing not correctly and can respond to corrections for future troubleshooting.All mentioned above features totally allow us obtain qualitative VLW, which in teaching physics, executing project and investigating works can be used.
However, we must remember that VLW can not provide the total replacement of the real experiment.It simplifies and informs the educational process only.One has both advantages and disadvantages as a real experiment.
In paper [1] the analysis of experiment carried out with Galilei pendulum and realized in "live physics" program medium has been presented.The created virtual model was escorted to the real physical equipment and allowed create the physical models and execute the numerical experiment.The practical work with Galilei pendulum is interesting for revealing equipment parameters by that a load hits an obstacle.This phenomenon can be realized easily in the virtual constructor with consequent realization in the demonstrating equipment.There it should be noted that developed posters and virtual models are using actively as the lecture demonstrations.
In paper [2] the features of using of VLW on physics in duration of pandemics (2019-2012) have been described where the main advantages and disadvantages using VLW during distance learning have been listed.In another paper [3] the possibilities of using VLW on nuclear physics have been presented where the main advantages of VLW for analyzing experimental results by plotting graphics and diagrams have been listed.
The important feature of VLW is that the teacher instead of the role active lecturer in the traditional lessons in these lessons transforms to the passive assistant for pupils in the modern educational process [4].
In the present paper the analysis of experiments carried out at school 55 of Sergeli district of Tashkent city in duration of April-May 2022 with 11 grade pupils has been presented [5][6][7][8][9].The aim of experiments was testing the mastery level of pupils by using the VLW on physics.For reaching this aim we made a decision the following tasks: 1. development of method for formation and development mastery of the subject by pupils when using VLW on the physics lessons; 2. testing investigation of level of perception by pupils on using VLW on physics lessons; 3. analysis of experiments results.

Experimental method
Before beginning experiments we made questioning teachers on physics of Tashkent city on "Using virtual laboratory works on physics at school" title, in which 15 teachers have been participated.From the survey of selected teachers became clear that expediency of using VLW on parts of atomic and nuclear physics in the educational process is indisputable.That end we proposed pupils do laboratory work on atomic physics part, in which Rutherford experiences using α-particles for defining atomic structure have been explained.We suggested pupils use "PHET" medium of Internet.Explain the essence of Rutherford experiences in duration of one lesson impossible practically because of phenomena dealing with in experiences take place on a scale approximately 10 -10 meter, in which it is required differ distances about 10 -13 meter, that is hard to imagine.The situation is further complicated by that α-particles fly out from source with speed about 30000 kilometers/second (supposedly)!For pupils speed of cars about 200 kilometers/hour even is very high, at the same time α-particles acquire about 500000 times (!) higher speed in comparison of speed of cars.
Further, analysis of the knowledge results by pupils obtained at the beginning of following lesson on physics by testing showed that in 11A grade class of school 55, where VLW on Rutherford experiences was used, mastery of the topic was much better compared with 11B grade class of the same school.From 31 of 11A class pupils 11 ones rated "Excellent", 16 -"Good", 4 -"Satisfactory", 0 -"Unsatisfactory".And in 11B class where lesson carried out in the traditional form, that is without using VLW, from 33 pupils 2 ones rated "Excellent", 6 -"Good", 12 -"Satisfactory", 13 -"Unsatisfactory".
However, "PHET" medium allows demonstrate pupils in the model representation with the real consequently events with differences only in increasing atomic scale up to several centimeters and decreasing speed of α-particles about million times.All these allow pupils much easier to imagine throwing small balls instead of α-particles to side of the mice instead of atoms.
The process snapshot of Rutherford experiences with α-particles has been presented on Figure 1.Here atoms (with diameter about 10 -10 meter) are presented as transparent big sphere, in center which nuclear (with diameter about 10 -13 meter) as a yellow color point is marked.α-particles in the monitor are marked as violet points.There is also hitch dealing with the comparable scale of nuclear and α-particles: theirs real sizes differ about hundred times as the same time in monitor they are plotted almost the same.
Pupils can control processes by variation of α-particles energy, protons and neutrons quantities in nuclear and observe mouse shot processes.In order to represent more correctly the sizes in comparison of atomic nuclear and αparticles we must remove out of sight of atom totally (see, Figure 2).However, there pupils can see the nuclear and α-particles structures, consisting protons (white balls) and neutrons (pink balls).

Conclusion
Thus, from the analysis of experimental results carried out on revealing expediency for using VLW in the physics lessons we can conclude that: In "PHET" medium is possible transfer visually the atomic scales with about 10 -10 meter to several centimeters and nuclei size with about 10 -13 meter to dot sizes with about tenth part of millimeter.There is possibility decrease visually the speed of α-particles from values about 30000 kilometers/second almost million times too.This procedure allows us observe processes of α-particles decay in the atomic mouse in the model representation with the logical consequent events.
Of course, there is need to transfer events dealing in three dimensional space to two dimension plane too, which in its turn also makes it difficult to perceive a lesson by pupils.We shell expect that soon this problem will be solved too and pupils will have possibility to observe the model processes in VLW from the different sides of three dimensional space and time.

Fig. 1 .
Fig.1.Photo from virtual laboratory work of Rutherford experiences with α-particles from "PHET" medium

Fig. 2 .
Fig. 2. Representation more correctly the sizes in comparison of atomic nuclear and α-particles