Lab Methods

Some famous experiments you may be asked about:

Experimental apparatus and methods:

Problem 1:

Which of the following measure the charge of an electron independent of its mass?

(A)  Millikan oil-drop experiment
(B)  Thompson experiment
(C)  Bragg scattering
(D)  Cyclotron resonance
(E)  Compton effect

Problem 2:

High energy gamma rays can be produced by backscattering laser light from a beam of very high energy electrons.  This method depends on the properties of

(A)  Rayleigh scattering
(B)  Thompson scattering
(C)  Bragg scattering
(D)  Raman scattering
(E)  Compton scattering

Problem 3:

Stern and Gerlach succeeded in deflecting a beam of silver atoms with an inhomogeneous magnetic field.  Which of the following is a generally accepted interference from the result of their measurement?

(A)  The technique is useful for precise measurements of magnetic field intensities.
(B)  The simple deflection observed is principally due to an induced magnetic moment in the silver atoms.
(C)  The two deflections observed are due to the two possible values of a component of the magnetic moment of the atom along any axis.
(D)  The three deflections observed are due to neutral atoms, negatively charged ions, and positively charged ions.
(E)  The continuous range of values observed is due to random orientations of the magnetic moments of the atoms.

Problem 4:

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The circuit shown contains a resistor whose resistance is R with and uncertainty ΔR and a battery of emf ε with uncertainty Δε.  The uncertainties are uncorrelated.  What is the uncertainty in the power dissipated in the resistor?

(A)  (Δε/ε +  R/R) ε2/R    (B)  [(Δε/ε)2 + (ΔR/R)2]1/2 ε2/R
(C)  (Δε/ε - ΔR/R) ε2/R    (D)  (2Δε/ε - ΔR/R) ε2/R  
(E)  [4(Δε/ε)2 + (ΔR/R)2]1/2 ε2/R  

Problem 5:

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Which of the following circuits will have the v-i characteristic shown.  (All diodes are silicon.)

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Problem 6:

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The gain of an amplifier is plotted versus frequency ω in the diagram.  If K is a positive constant the frequency dependence of the gain near ω = 3*105/s is most accurately expressed by

(A)  K e-aω    (B)  Kω2    (C)  Kω    (D)  Kω-1    (E)  Kω-2

Problem 7:

An experimenter measures the counting rate from a radioactive source to be 10150 counts in 100 minutes.  without changing any of the conditions, the experimenter counts for one minute.  There is a probability of about 15% that the number of counts recorded will be fewer than

(A)  50    (B)  70    (C)  90    (D)  100    (E)  110

Problem 8:

A beam of particles is incident on a thin target of thickness t.  If the cross section per nucleus for scattering of the particles by the nuclei of the target is σ, and the number of nuclei per unit volume is n, the fraction of particles scattered is

(A)  σ/nt   (B)  σt    (C)  ntσ    (D)  nt/σ    (E)  nt

Problem 9:

The initial intensity I0 of a beam of photons of a certain energy is reduced to (1/2)I0 as the beam traverses a thin sheet of lead of thickness d.  If the beam traverses a sheet of lead of thickness 3d, its intensity is reduced to

(A)  (1/3)I0   (B)  (1/4)I0    (C)  (1/6)I0    (D)  (1/8)I0    (E)  (1/8)I0

Problem 10:

The resolving time of a counter is 2.5*10-6 s and the dead time of the recording device is 3*10-4 s.  If the number of incident particles is 5*103/s, the number of recorded particles is closest to

(A)  1*103/s  (B)  2*103/s    (C)  3*103/s   (D)  4*103/s   (E)  5*103/s