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General Certificate of EducationJanuary 2005Advanced Subsidiary Examination

PHYSICS (SPECIFICATION A) PA01Unit 1 Particles, Radiation and Quantum Phenomena

Wednesday 12 January 2005 Morning Session

In addition to this paper you will require:! a calculator;! a pencil and a ruler.

Time allowed: 1 hour

Instructions! Use blue or black ink or ball-point pen. ! Fill in the boxes at the top of this page. ! Answer all questions in the spaces provided. All working must be shown.! Do all rough work in this book. Cross through any work you do not want

marked.

Information! The maximum mark for this paper is 50. ! Mark allocations are shown in brackets. ! The paper carries 30% of the total marks for Physics Advanced Subsidiary

and carries 15% of the total marks for Physics Advanced.! A Data Sheet is provided on pages 3 and 4. You may wish to detach this

perforated sheet at the start of the examination. ! You are expected to use a calculator where appropriate.! In questions requiring description and explanation you will be assessed on

your ability to use an appropriate form and style of writing, to organiserelevant information clearly and coherently, and to use specialist vocabularywhere appropriate. The degree of legibility of your handwriting and the levelof accuracy of your spelling, punctuation and grammar will also be taken intoaccount.

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Examiner�s Initials

Leave blankSurname Other Names

Centre Number Candidate Number

Candidate Signature

PA01

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Data Sheet

! A perforated Data Sheet is provided as pages 3 and 4 of this question paper.

! This sheet may be useful for answering some of the questions in the examination.

! You may wish to detach this sheet before you begin work.

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Data Sheet

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Answer all questions in the spaces provided.

1 (a) Name the constituent of an atom which

(i) has zero charge,

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(ii) has the largest charge to mass ratio,

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(iii) when removed leaves a different isotope of the element.

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(b) An α particle is the same as a nucleus of helium, He.The equation

Th Ra + α

represents the decay of thorium by the emission of an α particle.

Determine

(i) the values of X and Y, shown in the equation,

X = .....................

Y = .....................

(ii) the ratio mass of Ra nucleus

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XY

XY

22990

42

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.mass of α particle

2 The diagram shows some of the electron energy levels of an atom.

level energy/10�18J

D �0.21

C �0.44

B �0.90

(ground state) A �1.94

An incident electron of kinetic energy 4.1 × 10�18J and speed 3.0 × 106m s�1 collides with the atomrepresented in the diagram and excites an electron in the atom from level B to level D.

(a) For the incident electron, calculate

(i) the kinetic energy in eV,

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(ii) the de Broglie wavelength.

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(b) When the excited electron returns directly from level D to level B it emits a photon.Calculate the wavelength of this photon.

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3 (a) (i) Name a force which acts between an up quark, u, and an electron. Explain, with referenceto an exchange particle, how this force operates.

You may be awarded marks for the quality of written communication in your answer.

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(ii) With what particle must a proton collide to be annihilated?

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(b) A sigma plus particle, Σ+, is a baryon.

(i) How many quarks does the Σ+ contain?

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(ii) If one of these quarks is an s quark, by what interaction will it decay?

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(iii) Which baryon will the Σ+ eventually decay into?

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4 The equation

p n + β + + νe

represents the emission of a positron from a proton.

(a) Energy and momentum are conserved in this emission.What other quantities are conserved in this emission?

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(b) Draw the Feynman diagram that corresponds to the positron emission represented in theequation.

(4 marks)

(c) Complete the following table using ticks "and crosses ×.

(4 marks)

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particle fundamental meson baryon leptonparticle

pn

β+

νe

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5 (a) The photoelectric effect is represented by the equation

hf = φ + Ek.

What does Ek represent?

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(b) A metal plate is illuminated with electromagnetic radiation of wavelength 190 nm. The metalhas a work function of 7.9 × 10�19J.

(i) Calculate the frequency of the incident electromagnetic radiation.

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(ii) Show that the metal plate will emit photoelectrons when illuminated with radiation of thiswavelength.

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(iii) The radiation incident on the metal plate remains at a constant wavelength of 190 nm butits intensity is now doubled. State and explain the effect this has on the emitted photoelectrons.

You may be awarded marks for the quality of written communication in your answer.

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6 The diagram, which is not to scale, shows the cross-section of a 45° right angled glass prism supportedby a film of liquid on a glass table. A ray of monochromatic light is incident on the prism at an angleof incidence θ and emerges along the glass � liquid boundary as shown.

refractive index of glass = 1.5

(a) Calculate the speed of light in the glass.

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(b) Determine

(i) the angle of incidence, θ,

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(ii) the refractive index of the liquid.

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air

glass

emergent ray

glass

liquidA

60°45°

15°

θ

(c) The liquid is now changed to one with a lower refractive index. Draw a possible path for the raybeyond the point A and into the air. (2 marks)

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END OF QUESTIONS

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QUALITY OF WRITTEN COMMUNICATION (2 marks)

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