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Particle Physics - General Physics - Solved Exam, Exams of Physics

Birla Institute of Technology and SciencePhysics

This is the Solved Exam of General Physics which includes Vector Quantities, Scalar Quantities, Resultant of Two Vectors, Circumference of Circle, Newton’s Second Law of Motion, Magnitude and Direction etc. Key important points are: Particle Physics, Particle Accelerators, Cockroft and Walton Experiment, Alpha Particles, Advantage of Circular Accelerators, Linear Accelerators, Nuclear Equation for Decay

Typology: Exams

2012/2013

Uploaded on 02/19/2013

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Exam Questions
mass of proton = 1.6730 × 10-27 kg; mass of electron = 9.1 × 10–31 kg;
mass of lithium nucleus = 1.1646 × 10-26
kg; mass of α-particle = 6.6443 × 10-27 kg;
mass of neutron = 1.6749 × 10–27 kg; charge on electron = 1.6022 × 10–19 C;
mass of pion = 2.4842 × 10–28 kg;
speed of light, c = 2.9979 × 108 ms-1; Planck constant = 6.626 × 10-34 J s
Particle Accelerators, Cockroft and Walton Experiment and E = mc2
1. [2009]
In 1932 Cockcroft and Walton succeeded in splitting lithium nuclei by bombarding them with
artificially accelerated protons using a linear accelerator.
Each time a lithium nucleus was split a pair of alpha particles was produced.
(i) How were the protons accelerated?
(ii) How were the alpha particles detected?
2. [2005]
High voltages can be used to accelerate alpha particles and protons but not neutrons.
Explain why.
3. [2009]
Most of the accelerated protons did not split a lithium nucleus. Explain why.
4. [2002]
In 1932, Cockcroft and Walton carried out an experiment in which they used high-energy protons to
split a lithium nucleus. Outline this experiment.
5. [2007]
(i) Draw a labelled diagram to show how Cockcroft and Walton accelerated the protons.
(ii) What is the velocity of a proton when it is accelerated from rest through a potential difference of 700
kV?
6. [2009] [2007] [2005][2002]
Write a nuclear equation to represent the splitting of a lithium nucleus by a proton.
7. [2009] [2007][2002]
Calculate the energy released in this reaction.
8. [2005][2009]
Circular particle accelerators were later developed.
Give an advantage of circular accelerators over linear accelerators.
9. [2004]
In beta decay, a neutron decays into a proton with the emission of an electron.
Write a nuclear equation for this decay.
10. [2004
Calculate the energy released during the decay of a neutron.
The neutrino
11. [2008]
The existence of the neutrino was proposed in 1930 but it was not detected until 1956.
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Exam Questions mass of proton = 1.6730 × 10-27^ kg; mass of electron = 9.1 × 10–31^ kg; mass of lithium nucleus = 1.1646 × 10-26^ kg; mass of α-particle = 6.6443 × 10-27^ kg; mass of neutron = 1.6749 × 10–27^ kg; charge on electron = 1.6022 × 10–19^ C; mass of pion = 2.4842 × 10–28^ kg; speed of light, c = 2.9979 × 10^8 ms-1; Planck constant = 6.626 × 10-34^ J s

Particle Accelerators, Cockroft and Walton Experiment and E = mc^2

  1. [2009] In 1932 Cockcroft and Walton succeeded in splitting lithium nuclei by bombarding them with artificially accelerated protons using a linear accelerator. Each time a lithium nucleus was split a pair of alpha particles was produced. (i) How were the protons accelerated? (ii) How were the alpha particles detected?
  2. [2005] High voltages can be used to accelerate alpha particles and protons but not neutrons. Explain why.
  3. [2009] Most of the accelerated protons did not split a lithium nucleus. Explain why.
  4. [2002] In 1932, Cockcroft and Walton carried out an experiment in which they used high-energy protons to split a lithium nucleus. Outline this experiment.
  5. [2007] (i) Draw a labelled diagram to show how Cockcroft and Walton accelerated the protons. (ii) What is the velocity of a proton when it is accelerated from rest through a potential difference of 700 kV?
  6. [2009] [2007] [2005][2002] Write a nuclear equation to represent the splitting of a lithium nucleus by a proton.
  7. [2009] [2007][2002] Calculate the energy released in this reaction.
  8. [2005][2009] Circular particle accelerators were later developed. Give an advantage of circular accelerators over linear accelerators.
  9. [2004] In beta decay, a neutron decays into a proton with the emission of an electron. Write a nuclear equation for this decay.
  10. [ Calculate the energy released during the decay of a neutron.

The neutrino

  1. [2008] The existence of the neutrino was proposed in 1930 but it was not detected until 1956.

Give two reasons why it is difficult to detect a neutrino.

  1. [2007] In beta decay it appeared that momentum was not conserved. How did Fermi’s theory of radioactive decay resolve this?
  2. [2004] Momentum and energy do not appear to be conserved in beta decay. Explain how the existence of the neutrino, which was first named by Enrico Fermi, resolved this. Antimatter
  3. [2007] Compare the properties of an electron with that of a positron.
  4. [2007] What happens when an electron meets a positron?
  5. [2003] Give one contribution made to Physics by Paul Dirac.

Pair Production

  1. [2005] In an accelerator, two high-speed protons collide and a series of new particles are produced, in addition to the two original protons. Explain why new particles are produced.
  2. [2009] Cockcroft and Walton’s apparatus is now displayed at CERN in Switzerland, where very high energy protons are used in the Large Hadron Collider. In the Large Hadron Collider, two beams of protons are accelerated to high energies in a circular accelerator. The two beams of protons then collide producing new particles. Each proton in the beams has a kinetic energy of 2.0 GeV. (i) Explain why new particles are formed. (ii) What is the maximum net mass of the new particles created per collision?
  3. [2008] (i) In a circular accelerator, two protons, each with a kinetic energy of 1 GeV, travelling in opposite directions, collide. After the collision two protons and three pions are emitted. What is the net charge of the three pions? Justify your answer. (ii) Calculate the combined kinetic energy of the particles after the collision. (iii) Calculate the maximum number of pions that could have been created during the collision.
  4. [2003] The following reaction represents pair production: γ → e+^ + e– Calculate the minimum frequency of the γ-ray photon required for this reaction to occur.
  5. [2003] What is the effect on the products of a pair production reaction if the frequency of the γ-ray photon exceeds the minimum value?

Pair Annihilation

  1. [2006] During a nuclear interaction an antiproton collides with a proton.

Fundamental Forces

  1. [2008] Baryons and mesons are made up of quarks and experience the four fundamental forces of nature. List the four fundamental forces and state the range of each one.
  2. [2006] List the fundamental forces of nature that pions experience.
  3. [2005] Name the fundamental force of nature that holds the nucleus together.
  4. [2004] Beta decay is associated with the weak nuclear force. List two other fundamental forces of nature and give one property of each force.
  5. [2002] Name the four fundamental forces of nature.
  6. [2002] Which force is responsible for binding the nucleus of an atom?
  7. [2009] Arrange the fundamental forces of nature in increasing order of strength.
  8. [2002] Give two properties of the strong force.

Quark Composition and Particle Classification

  1. [2008] Name the three positively charged quarks.
  2. [2008] What is the difference in the quark composition of a baryon and a meson?
  3. [2008] What is the quark composition of the proton?
  4. [2007] A kaon consists of a strange quark and an up anti-quark. What type of hadron is a kaon?
  5. [2006] Pions are mesons that consist of up and down quarks and their antiquarks. Give the quark composition of (i) a positive pion, (ii) a negative pion.
  6. [2006] Name the three negatively charged leptons.
  7. [2004] Give the quark composition of the neutron.
  8. [2005]

A huge collection of new particles was produced using circular accelerators. The quark model was proposed to put order on the new particles. List the six flavours of quark.

  1. [2005] Give the quark composition of the proton.
  2. [2003] Leptons, baryons and mesons belong to the “particle zoo”. Give (i) an example, (ii) a property, of each of these particles.
  1. The kinetic energy of the two protons gets converted into mass.

(i) When the protons collide into each other they lose their kinetic energy and it is this energy which gets converted into mass to form the new particles. (ii) Total energy = 4 GeV E = mc^2 ⇒ m = E/ c^2 ⇒ m = (4 × 10^9 ) (1.6 × 10-19)/(2.9979 × 10^8 )^2 ⇒ m = 7.121 × 10-27^ kg

(i) Zero, because electric charge must be conserved. (ii) Energy equivalent of a pion:) E = mc^2 E = (2.4842 )( 2.9979 × 10^8 )^2 E = 2.2327 × 10–11^ J = 1.3935 × 10^8 eV For 3 pions E = 6.6980 × 10–11^ J = 4.18047 × 10^8 eV Energy after collision = (2 × 10^9 ) - (4.18047 × 10^8 ) = 1.58195 × 10^9 eV = 2.535 × 10– (^10) J

(iii)Number of pions = (1.58195 × 10^9 ) / 1.3935 × 10^8 = 11.3524 = 11 pions. Maximum number of pions = 3 + 11 = 14 pions.

  1. E = (2)mc^2 = hf 2(9.1 × 10–31)( 3.0 × 10^8 )^2 = (6.6 × 10–34)f ⇒ f = 2.5×10^20 Hz
  2. The electrons which were created would move off with greater speed. There may also be more particles produced.

(i) A photon is a discrete amount of electromagnetic radiation. (ii) m [= mass of proton + mass of antiproton ] = 2(1.673 × 10-27) = 3.346 × 10-27^ kg E = mc^2 = (3.346 × 10-27^ )(2.998 × 10^8 )^2 = 3.0074 × 10- Energy for one photon = 1.5037 × 10-10^ J E = hf ⇒ f = E/h / = 1.5037 × 10-10^ / 6.626 × 10-34^ = 2.2694 × 10^23 Hz (iii)So that momentum is conserved. (iv) They move in opposite directions. (v) Total charge before = +1-1 = 0 Total charge after = 0 since photons have zero charge (vi) The energy of the photons is converted into matter.

(i) e+^ + e-^ → 2γ (ii) Total charge on both sides is zero Momentum of positron + electron = momentum of photons

  1. Strong (short range), Weak (short range), Gravitational (infinite range), Electromagnetic (infinite range).
  2. Electromagnetic, strong, weak , gravitational
  3. The strong nuclear force.
  4. Strong: acts on nucleus/protons + neutrons/hadrons/baryons/mesons, short range Gravitational: attractive force, inverse square law/infinite range, all particles Electromagnetic: acts on charged particles, inverse square law/infinite range
  5. Gravitational, Electromagnetic, Strong (nuclear), Weak (nuclear)
  6. Strong
  1. Gravitational, weak, electromagnetic, strong.
  2. Short range, strong(est), act on nucleons, binds nucleus
  3. Up, top, charm
  4. Baryon: three quarks Meson: one quark and one antiquark
  5. Up, up, down
  6. It is a meson.
  7. π+^ = up and anti-down π-^ = down and anti-up
  8. Electron ( e ) , muon ( μ ), tau ( τ )
  9. Up, down, down
  10. Up, down, strange, charm, top and bottom.
  11. Up, up, down.
  12. LEPTONS; electron, positron, muon , tau, neutrino Not subject to strong force BARYONS; proton, neutron Subject to all forces, three quarks MESONS pi(on), kaon Subject to all forces, mass between electron and proton, quark and antiquark

[2010] Give two advantages of a circular accelerator over a linear accelerator. Smaller (less space) // greater speeds/energy

[2010]

(i) What is anti-matter? Antimatter is material/matter/particles that has same mass as another particle but opposite charge.

(ii) An anti-matter particle was first discovered during the study of cosmic rays in 1932. Name the anti-particle and give its symbol. positron / anti-electron

(iii)What happens when a particle meets its anti-particle? Pair annihilation occurs and the mass gets converted to energy.

(iv) What is meant by pair production? Pair production involves the production of a particle and its antiparticle from a gamma ray photon.

(v) A photon of frequency 3.6 × 10^20 Hz causes pair production. Calculate the kinetic energy of one of the particles produced, each of which has a rest mass of 9.1 × 10–31^ kg.