1 Lab skills core examination

1.1

Suppose that a set of measurements of x in the lab are found to be normally distributed with a mean of μ and standard deviation σ. What is the probability that any one of them will fall between μ - σ and μ + σ?
A. 0.11, B. 0.49, C. 1.0, D. 0.89, E. 0.5

1.2

Individual nuclear decays of substance X are low probability events, ℘ = 1.0 × 10^-23 for decay within a ten second interval. The number of decays in 10 second intervals coming from a sample are distributed according to a Poisson distribution. If the sample contains 0.333moles of substance X, hat is the probability of detecting 4 decays within a ten second interval?
A. 1.0, B. 0.135, C. 0.125, D. 0.667, E. 0.09

1.3

For the nuclear decay experiment of the previous problem, what is the mean number of decays that will be detected within a ten second period?
A. 1, B. 2, C. 3, D. 4, E. 5

1.4

Suppose that we measure the critical angle for a static equilibrium on an inclined plane, and discover that motion begins at angle θ = 0.12000, 0.12300, 0.11900, 0.12100, 0.12000, 0.12100 radians for six trials. The coefficient of friction computed from this is then

1.5

In a lab you make many measurements {a₁,a₂,,a_N}, {b₁,b₂,,b_N} of quantitis a and b, obtaining means , with standard deviations σ_a,σ_b respectively.
From these you commpute quantity c = a² + b. What should you report as the experimentally established value of c?
A. , B. ² + , C. You would need to actually measure c to do this, D. Either A or B, since they are the same, E. The correct answer is not listed as a choice.

1.6

In the previous problem, what should be reported as the error (standard deviation) in the determination of c from this data?
A. , B. ∑ _i=1^N- (a_i² + b _i)²,, C. , D. , None of these are correct.

1.7

Suppose that you wish to verify the hypothesis that x = , you make four measurements of y(x); {y(1) = 2.2,y(2) = 2.93,y(4) = 4.1,y(9) = 6.2}. Determine the value of χ² for this data.
A. 3.27, B. 0.327, C. 0.0327, D. 0.0171, E. 0.171

1.8

In the previous problem, which of the measurements will have the largest influence on χ²? This translates into; which measurement will probably be the deciding factor in the confidence of the verification of the hypothesis?
A. That of y(1), B. That of y(2), C. That of y(4), D. That of y(9), E. All are equally significant.

1.9

In the verification of a hypothesis in the lab, experimental data, when compared to theoretical predictions, produces a χ² = 0.432 for a set of N measurements. You consult a table of Chi-squared probability functions, and determine that for this N, ℘(χ² ≥ 0.432) = 0.9231. What does this mean?
A. The probability is 0.9231 that a set of random measurements will have a smaller χ² than yours, B. The probability is 0.9231 that a set of random measurements will have a bigger χ² than yours, C. The probability is 0.9231 that you should repeat all measurements, D. The probability is 0.9231 that you should never set foot in the lab again, E. The probability is 0.9231 that you should become a theoretician.

1.10

What is the median of a distribution of data?
A. Same as the mean, B. The point below which half of the data points lie, C. The point of maximal probability, D. The point of minimal probability, E. None of these.

1.11

What is the mode of a Chi-squared probability distribution for N data points?
A. N - 2, B. N - 1, C. N, D. N + 1, C. N + 2,

1.12

What is the slope of the line that best fits these points; {(x,y) = (1.0, 2.0), (2.0, 3.3), (3.0, 4.0)}?
A. 1.0, B. 1.3, C. 1.5, D. 1.1, E. 1.15

1.13

What is the intercept of the line that best fits these points; {(x,y) = (1.0, 2.0), (2.0, 3.3), (3.0, 4.0)}?
A. 1.0, B. 1.3, C. 1.5, D. 1.1, E. 1.15

1.14

1.15

The photon emitted in the decay process ₅₆¹³⁷Ba → ₅₆¹³⁷Ba + γ has an energy in the range of
A. A few eV , B. A few keV , C. Hundreds of keV , D. Thousands of keV , E. Less than 1eV .

1.16

The photon emitted in the atomic process H^* → H + γ has an energy in the range of
A. A few eV , B. A few keV , C. Hundreds of keV , D. Thousands of keV , E. Less than 1eV .

1.17

Which process below is producing α-radiation?
A. p⁺ + e^- → n⁰ + ν _e, B. n⁰ → p⁺ + e^- + _e, C. _m^pX → _m-2^p-4Y + ₂⁴He, D. e⁺ + e^- → 2γ, E. None of these.

1.18

Which process below is producing β-radiation?
A. p⁺ + e^- → n⁰ + ν _e, B. n⁰ → p⁺ + e^- + _e, C. _m^pX → _m-2^p-4Y + ₂⁴He, D. e⁺ + e^- → 2γ, E. None of these.

1.19

Which process below is called the β-decay?
A. p⁺ + e^- → n⁰ + ν _e, B. n⁰ → p⁺ + e^- + _e, C. _m^pX → _m-2^p-4Y + ₂⁴He, D. e⁺ + e^- → 2γ, E. None of these.

1.20

A nuclear decay rate for a sample has a half-life of 100 s. How long will it take the activity of a sample to drop from 512 Bq to 32 Bq?
A. 400s, B. 300s, C. 200s, D. 100s, E. 50s

1.21

Nuclei with filled nuclear shells are super-stable. A nucleus with atomic number Z with filled nuclear shells is a nucleus whose Z is a magic number. Which value of Z listed below is not magic?
A. 2, B. 8, C. 16, D. 20, E. 40

1.22

Consider a nucleus whose protons and neutrons are contained in filled nuclear shells. What is the nuclear spin of such a nucleus?
A. 0, B. , C. 1, D. , E. 2,

1.23

1.24

Use the shell-model energy levels of the previous problem to determine the nuclear spin of ₄⁷Li.
A. 0, B. , C. 1, D. , E. 2

1.25

In actual fact, shell-model neutron states lie slightly lower in energy than corresponding proton states. Why?
A. Coulomic repulsion raises proton energy, B. Coulomic repulsion lowers neutron energy, C. Most nuclei have more n than p, D. Attraction between p and atomic e^- raises the proton energy, Nuclear forces among neutrons is greater than that between protons.

1.26

The speed of sound in air at 273K is 331. Raising the air temperature by one degree has what effect on the speed of sound?
A. None, B. Lowers it by about 0.6, C. Lowers it by about 1.3, D. Raises it by about 0.6, E. Raises it by about 1.3

1.27

The adiabatic constant of a diatomic molecule should be
A. k, B. k, C. k, D. k, E. k

1.28

The adiabatic constant of a triatomic molecule should be
A. k, B. k, C. k, D. k, E. 1.22k

1.29

Consider a diatomic molecule at very low temperatures, as the temperature is raised, what will be the order in which molecular modes are excited (first/next/last)?
A. rotational/translational/vibrational, B. vibrational/rotational/translational, C. vibrational/translational/rotational, D. translational/vibrational/rotational, E. translational/rotational/vibrational

1.30

Consider an electron diffraction experiment, in which electrons are to bombard a crystalline powder. Describe the resulting diffraction pattern produced by scattered electrons stricking a phosphorescent screen.
A. It will consist of lines, B. It will consist of a lattice of points, C. It will consist of concentric rings, D. Whether we see points, lines or rings will depend on the crystal structure, E. None of these are correct.

1.31

Typical interatomic spacings in common crystalline solids are about how large?
A. A few fermi, B. A few Angstroms, C. A few nanometers, D. A few micrometers, E. A few picometers.

1.32

1.33

The crystal structure illustrated is a single primitive cell for NaCl. The entire lattice structure of the crystal, made by stacking these cells, is invariant under all translations of the form = m + n + p , m,n,p being integers.

1.34

In the single primitive cell of NaCl, what lies at the point 000?
A. A Sodium, B. A Chlorine, C. Empty space, D. A lattice defect, None of these things.

1.35

According to the rule of lattice symmetry, when more cells are stacked around this one, what will lie at the points + m + n + p , m,n,p being integers?
A. A Sodium, B. A Chlorine, C. Empty space, D. A lattice defect, None of these things.

1.36

In electron scattering from a poly-crystalline powder, what do the electrons actually scatter off of, or diffract from?
A. The nuclei of the solid, B. The lattice points of the crystal structure, C. Planes of atoms, D. Slits or aperatures between atoms, E. They liberate electrons from the solid, which creates interference patterns.

1.37

In the photoelectic effect, how large is a tyical work function for photo-sensitive metals?
A. < 0.01eV , B. ≈ 0.1eV , C. ≈ 1.0eV , D. > 10.0eV , E. > 100.0eV

1.38

In the Franck-Hertz experiment, a beam of electrons is passed through a gas of Helium atoms at very low pressure. Electrons arrive at an anode, and this anode current is monitored as a function of the accelerating voltage V ₀ = (V _c -V _a) applied to the electrons. The anode current I_a is a good measure of the energy of the electrons arriving at the anode. If the Franck-Hertz tube is completely evacuated (no Helium), we should expect
A. I_a increases as V ₀ increases, B. I_a decreases as V ₀ increases, C. I_a stays constant as V ₀ increases, D. I_a → 0 with no Helium. E. None of these.

1.39

With the Franck-Hertz tube filled with Helium, What should happen to I_a when the accelerating voltage V ₀ is such that eV ₀ = ΔE, where ΔE is an electronic excitation energy of the Helium?
A. It should drop suddenly, B. It should rise suddenly, C. It should stay constant, D. None of these are correct, E. I have decided not too study physics after all, is the psychology office on this floor?

1.40

1.41

To calibrate the MCA, one would need to translate photon counter channel into photon energy, assuming a relation of ch = a + E_γb. To do this we would need to count photons from two well known gamma ray sources. ⁶⁰Co provides two photons, E ₁ = 1173.2 KeV , and E₂ = 1332.47 KeV that come in at channels ch₁ = 837 and ch₂ = 947. Calibrate this MCA, and determine the energy of the Compton edge seen when the scintillator is exposed to ¹³⁷Cs gamma rays; the photopeak occurs at ch_γ = 476, the edge at ch_edge = 345.
A. 461 KeV , B. 662 KeV , C. 477 KeV , D. 650 KeV , E. 1001 KeV

1.42

1.43

The particles collected by the photocathode cause the photocathode to emit particles itself into the lower stages of the tube. What are these particles?
A. Electrons, B. Holes, C. Neutrinos, D. Photons, E. Protons.

1.44

The dynodes in the lower portion of the tube amplify the signal created by the photocathode ejection by what effect?
A. Mossbauer, B Joule-Thompson, C. Photoelectric, D. Compton, E. Ramsauer.

1.45

In order to measure the current through a device in a circuit with an ammeter, you must
A. Connect the meter in parallel with the device, B. Break the circuit, and connect the meter in series, C. Simply place the meter next to the device, D. Replace the device with the meter, E. None of these.

1.46

In order to measure the voltage across a device in a circuit with an voltmeter, you must
A. Connect the meter in parallel with the device, B. Break the circuit, and connect the meter in series, C. Simply place the meter next to the device, D. Replace the device with the meter, E. None of these.

1.47

To measure the strength of a magnetic field on the order of 0.001T in the lab, a simple way to perform the measurement using only a voltmeter would be to use a
A. Compass, B. Flip-coil, C. interferometer, D. thermistor, E. Hall probe IC

1.48

Suppose that you have one known mass, and an unknown mass. You could determine the unknown mass if you had (only)
A. A stopwatch and a spring, A known battery and a voltmeter, C. A graduated cylinder full of water, D. A length of string and a weight set, E. A meterstick and a stopwatch.

1.49

Suppose that you had a tuning fork of unknown vibrational frequency. You could measure the frequency if you had (only)
A. A stopwatch and a spring, A known battery and a voltmeter, C. A graduated cylinder full of water, D. A length of string and a weight set, E. A meterstick and a stopwatch.

1.50

Suppose that you had a block of wood of unknown vibrational density. You could measure the density if you had (only)
A. A stopwatch and a spring, A known battery and a voltmeter, C. A graduated cylinder full of water, D. A length of string and a weight set, E. A meterstick and a stopwatch.

1.51

A diffraction grating is essentially an N-slit interference slide with slit seperation d, and N very large. When illuminated with light of wavelength λ, what is the angular width of the interference fringes?
A. , B. , C. , D. , E. Nλ

1.52

A diffraction grating is the best all around tool for measuring unknown wavelengths λ₁ of light. To do so, it is illuminated ith the unknown wavelength light and a known wavelength λ₂ that is very similar simultaneously. If the m^th oder interference fringes of the two colors of light are seperated by the value found in the previous problem, both fringes will be visible, discernibly seperate, and we say that the wavelengths are resolved in m^th order.
Sodium vapoer lamps produce light with wavelengths λ₁ = 589.00 nm and λ₁ = 589.59 nm. In order to resolve the sets interference fringes in third order, minimally how many slits (rulings) N must a diffraction grating have?
A. 330, B. 360, C. 430, D. 230, E. 133

1.53

In order to measure the location of a virtual image formed by lenses in an optical experiment, you should
A. Use a movable screen to capture the image, B. Simply calculate its location, since measuring it is impossible, C. Look for the point where image parallax vanishes, D. Find the point of maximal image parallax, E. Use a diffraction grating.

1.54

1.55

Which type of capacitor should never be connected to an AC voltage?
A. Polystyrene, B. electrolytic, D. Carbon-film, D. Metal-oxide-film, E. Ceramic

1.56

Doubling the temperature of a tempering oven is going to do what to the total electromagnetic energy within it?
A. Double, B. Quadruple, C. Increase eight-fold, D. Increase sixteen-fold, E. Nothing.

1.57

What is the lowest possible multipole electromagnetic radiation mode?
A. Monopole, B. Dipole, C. Quadrupole, D. Octupole, E. Hexadecapole.

1.58

What is the lowest possible multipole gravitational radiation mode?
A. Monopole, B. Dipole, C. Quadrupole, D. Octupole, E. Hexadecapole.