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12 th Class; Complete Course (11 th & 12 th Class) Algebra; Calculus; Trigonometry; Coordinate Geometry; Statistics; Physics. 3 Waves in pipes and strings. (a) Let the work function of the surface be f. If v be the frequency of the light falling on the surface, then according to Einstein's photoelectric equation, the maximum kinetic energy KEmax of emitted electron is given by. When a different source of light is used, it is found that the critical retarding potential is changed to 1.1 volt. Threshold wavelength is also called cut off wavelength. Now if the frequency of incident light is kept constant and its intensity is further increased, then the number of incident photons will increase which increases the number of ejected photo electrons so current in circuit increases and now in this case at higher intensity of incident light, current will not get saturated at potential difference VP1 as now due to more electron emission, space charge will be more and it will not vanish at VP1. Here we can see that at a particular reverse voltage V0, current in circuit becomes zero. When light of intensity I falls on a surface, it exerts force on that surface. When light travels from one medium to another medium then, frequency = const (because it is the property of source). your solution of Modern Physics, Chapter Notes, Class 12, Physics (IIT-JEE & AIPMT) | EduRev Notes search giving you solved answers for the same. This will help a student save time. At this time there was a great confusion about the nature of light which was solved by de-broglie from where origin of theory of matter wave come into picture. a particle) which he proved through balck body radiation spectrum. If the photo electrons (after emission from the surface) are subjected to a magnetic field of 10 tesla, what changes will be observed in the above two retarding potentials. 2nd Year Physics Notes include all 10 Chapters Short Questions, Long Questions, Past Paper Questions, Numericals, and Examples.. 1 Wave and motion. Thus one photon can not be absorbed by more than one electron. Class 12 Physics Index Page is provided here. Atomic Theory and the Evolution of the Atomic Model in General. 2. Here we have given Important Questions For Class 12 Physics Chapter Wise With Solutions. Find the work function of the emitting surface and the wavelength of second source. A high potential is applied to a discharge tube through a variable voltage source and a voltmeter and an ammeter are connected a measure the potential difference across the electrodes and to measure photoelectric current. 3. The study of Modern Physics is the study of the enormous revolution in our view of the physical universe that began just prior to 1900. The minimum amount of energy of photon required to eject an electron out of a metal surface is called work function It is denoted by φ. 1.11 Cut off Potential or Stopping Potential : We have seen with reverse polarity electrons are retarded in the discharge tube. In this case after ejection the kinetic energy of ejected electrons will be certainly less then . If we assume there are some electrons which do not loose any energy in the process of ejection, will come out from the metal surface with the maximum kinetic energy given as. 4 Acoustic phenomena. Here p is the momentum of photon. Find the work function for this metal. If f is the work function of the metal then there must be a minimum frequency of the incident light photon which is just able to eject the electron from the metal surface. Find the maximum impulse transmitted to the surface of the metal when each electrons flies out. Each photon has a definite energy and a definite linear momentum. This equation (8) is called Einstein's Photo Electric Effect equation which gives a direction relationship between the maximum kinetic energy stopping potential frequency of incident light and the threshold frequency. All the photons of a particular frequency or wavelength posses the same energy irrespective of the intensity of the radiation. During this interval the electron should be absorbing energy from the beam until it had accumulated enough to escape. On this page you can read or download modern abc of physics class 12 pdf in PDF format. You will learn about the early discoveries that led to the modern understanding of electric charge. The work function of tungsten cathode is, The maximum kinetic energy of ejected electrons can be given as. Business hours: Monday – Friday 10 AM – 6 PM. By continuing, I agree that I am at least 13 years old and have read and agree to the. Consider a radius about OZ to get a making an angle q with OZ. If a light beam of frequency n (each photon energy = hn) is incident on a metal surface having work function f then for , we have. In general, the term is used to refer to any branch of physics either developed in the early 20th century and onward, or branches greatly influenced by early 20th century physics. Remaining electrons which have relatively low kinetic energy will either be attracted to cathode just after ejection or will return during their journey from cathode to anode. Now, quantum theory solves these problems in providing the correct interpretation of the photoelectric effect. Threshold wavelength for the metal surface corresponding to work function 5.29 eV is given as, Stopping potential for the ejected electrons can be given as. Note that integration is done only for the hemisphere that faces the incident beam. Get all chapters and sub-topics of 12th standard physics of the National Council of Educational Research and Training textbook by visiting BYJU’S Class 8; Class 9; Class 10; Grade 11; Grade 12; Grade 12 Physics Chapters List. You can download Free Modern Physics, Chapter Notes, Class 12, Physics (IIT-JEE & AIPMT) | EduRev Notes pdf from EduRev by The reason for this is equation-(2) and (3). These notes are in PDF format that helps you to view the all chapters in one file. Thus we have. In graph II as frequency of incident light is more, the maximum kinetic energy of photoelectrons will also be high and to stop it high value of stopping potential is needed. Change q to q +dq and rotate the radius about OZ to get another circle on the sphere. This minimum frequency or threshold frequency vth can be given as. Modern physics is an effort to understand the underlying processes of the interactions with matter, utilizing the tools of science and engineering. It has gotten 25010 views and also has 4.8 rating. 1.10 Reversed Potential Across Discharge Tube : Now the experiment is repeated with charging the polarity of source across the discharge tube. Even at zero potential variable source, ammeter will show some current because due to the initial kinetic energy some electrons will reach the anode and cause some small current will flow. Beyond VP2, we can see that all the electrons ejected from cathode are reaching the anode are current become saturated at is2 because of more electrons. Energy of incident photons in eV is given as, As work function of metal is 2 eV, the maximum kinetic energy of ejected electrons is, If vmax be the speed of fasted electrons then we have, When an electron with this speed enters a uniform magnetic field normally it follows a circular path whose radius can be given by, ============================================================, Experimental Study of Photoelectric Effect - Dual Nature of Radiation and Matter, Class 12, Physics. So, go ahead and check the Important Notes for Class 12 Physics. (6) can be written as. Complete Assume absorption and reflection coefficient of surface be 'a' and 'r' and assuming no transmission. Here equation . If its speed is v2 at anode then we have. PHYSICS PRACTICAL CLASS 12 PDF: Modern’s ABC of Practical Physics Class 12 BEST CONSTRUCTION PROJECT MANAGEMENT SOFTWARE SOLUTIONS AND TOOLS Top Business Formation and legal Services Providing Company In this course, Amit Gupta will cover Wave Optics & Modern Physics for Class 12. This we can se from figure shown, that at higher intensity I2 (I2 > I1) current becomes saturated at higher value of potential difference VP2. Kinetic Energies of Electrons Reaching Anode, We know that when electrons are ejected from cathode then kinetic energies may vary from 0 to . Combining all these relations Eq. Michelson- Morley Experiment. The equation between Kmax and f is. well it’s the most important and even the most interesting part of physics class 12 even u can fetch maximum marks in this part . Thus all the electrons which are reaching anode will have speed less then or equal to vf. Sol. Structure Of An Atom All matter is made up of tiny particles known as atoms. 1. This is briefly described over here. In practical cases whenever an electron absorbs a photon from incident light, it comes out from the metal surface if but in process of ejection it may collide with the neighbouring electrons and before ejection it may loose some energy during collisions with the neighbouring electrons. The change in momentum is, Δp = 2 cosθ = Δt (ΔA cos2 q) (direction along ), The force on ΔA due to the light falling on it, is, The resultant force on the ring as well as on the sphere is along ZO by symmetry. This voltage V0, we can calculate from equation (1) by substituting vf = 0 hence. But as we know majority of ejected electrons have low values of kinetic energies which are collected outside the cathode and create a could of negative charge, we call space charge, as shown in figure shown. 1.12 Effect of Change in Frequency of Light on Stopping Potential : If we repeat the experiment by increasing the frequency of incident light with number of incident photons constant, the variation graph of current with voltage will be plotted as shown in figure shown. If you don't see any interesting for you, use our search form on bottom ↓ . Sol. But as in the two cases the kinetic energy of fastest electron are different as frequencies are different, the stopping potential for the two cases will be different. The variation of stopping potential with frequency v can be shown in figure shown. A photon is an energy packet which is fully absorbed not partially. RADIOACTIVITY . 1.8 Experimental Study of Photo Electric Effect : Experiments with the photoelectric effect are performed in a discharge tube apparatus as illustrated in figure shown. perfect preparation. This reverse potential difference V0 at which the fastest photoelectron is stopped and current in he circuit becomes zero is called cut off potential or stopping potential. Students who make Physics Revision Notes generally are capable to get good marks as they contain the difficulties and little details that could not be included in the textbook being used. If a uniform magnetic field of tesla is applied parallel to plate, what would be the radius of the path followed by electrons ejected normally from the plate with maximum energy. This current is1 is called saturation current. Now positive terminal of source is connected to the cathode of discharge tube. Those electrons which have high kinetic energies will rush toward, anode and may constitute the current in circuit. When a light beam incident on the cathode with , photoelectrons are ejected and move towards anode with negative polarity. Modern Physics, Chapter Notes, Class 12, Physics (IIT-JEE & AIPMT) | EduRev Notes notes for Class 12 is made by best teachers who have written some of the best books of 11 th Class; 12 th Class; Complete Course (11 th & 12 th Class) Kinematics & Rotational Motion; Modern Physics; Optics; Mechanics; Heat and Thermodynamics; Waves and Oscillations; Electricity and Magnetism; Chemistry. The modern era is the result of the progress in Physics, and its laws are interpreted every day … Ex.10 When a surface is irradiated with light of wavelength 4950 Å, a photo current appears which vanishes if a retarding potential greater than 0.6 volt is applied across the photo tube. There is no concept of photon conservation. Ex.5 Light of wavelength 1800 Å ejects photoelectrons from a plate of a metal whose work functions is 2 eV. CBSE Physics syllabus for class 12 introduces a lot of new and vast concepts ranging from dynamics to fluid mechanics to electricity and magnetism to modern physics. Learners at any … Ex.14 A perfectly reflecting solid sphere of radius r is kept in the path of a parallel beam of light of large aperture. All the important topics will be discussed in detail and would be helpful for the aspirants preparing for IIT JEE exam. By Einstein's energy mass relation, E = mc2 the equivalent mass m of the photon is given by. the following chapters come under modern physics: Atoms; Nuclei; Semiconductors and devices; Communication systems It supports dual nature of light (wave nature and particle nature). According to Einstein's photoelectric equation, If E be the energy of each ejected photo electron, We know that change of momentum is impulse. The NCERT Physics Books are based on the latest exam pattern and CBSE syllabus. A shown in graph, we can see as potential difference increases, current in circuit increases. of photons incident per unit time =Therefore, total change in momentum per unit time = n ΔP, force on photons = total change in momentum per unit time, Therefore, force on plate due to photon(F) = (downward), initial momentum of the photon = (downward), Therefore, energy incident per unit time = I A, Therefore, total change in momentum per unit time = n. DP, force = total change in momentum per unit time, (upward on photons and downward on the plate), When 0 < r < 1 a + r = 1, change in momentum of photon when it is reflected = (upward), change in momentum of photon when it is absorbed = (upward), force due to absorbed photon (Fa) = (downward), Force due to reflected photon (Fr) (downward). Light with frequency more than threshold frequency of cathode metal is incident on it, due to which photoelectrons are emitted from the cathode. If you want Modern Physics, Chapter Notes, Class 12, Physics (IIT-JEE & AIPMT) | EduRev Notes In this case the fastest electron ejected from cathode will be retarded during its journey to anode. EduRev is like a wikipedia 4. If the stopping potential is 1.3 V, find the work function of the metal. Calculate, (i) Maximum energy of emitted photoelectron and, (Mention both the results in electron-volts), Given Plank's constant joule-sec, joule and velocity of light, Sol. but, when maxwell asserted that light is a electromagnetic wave, scientists started believing that light is a wave. Let O be the centre of the sphere and OZ be the line opposite to the incident beam (figure). EduRev is a knowledge-sharing community that depends on everyone being able to pitch in when they know something. All photons of light of a particular wavelength l have the same energy and the same momentum p =. You can see some Modern Physics, Chapter Notes, Class 12, Physics (IIT-JEE & AIPMT) | EduRev Notes sample questions with examples at the bottom of this page. 6 Interference ,Diffraction and Polarisation. The exhaustive content provided for each of these subtopics will guide you through what you can expect to study in Class 12 Physics. Huygen was a scientist working parallel to Newton who come with a drastically different idea for nature of light & said that light is not a particle but a wave. Most of the concepts in class 12 physics are important as several higher level concepts are derived from the concepts that are introduced in … The concepts taught in the 12th standard are the fundamentals of the subject. (iii) The maximum velocity of the electrons ejected from the metal by light with a wavelength 1800 Å. Sol. A lot of the concepts in class 12 physics are really significant as many other higher level concepts are based on … Class Notes for Modern Physics, Part 1. 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