Lab Methods, solutions

Problem 1:  (A)

Famous experiments

Oil-drop experiment

Problem 2:  (E)

Famous experiments

Rayleigh scattering is the elastic scattering of electromagnetic radiation by particles much smaller than the wavelength of the radiation. Example: light scattering off individual atoms or molecules.  Rayleigh scattering is a function of the electric polarizibility of the particles.
Raman scattering is the inelastic scattering of electromagnetic radiation by particles much smaller than the wavelength of the radiation

Problem 3:  (C)

Famous experiments, frame transformation

Stern-Gerlach experiment

Problem 4:  (E)

Propagation of uncorrelated errors

P = ε2/R,  dP/P = 2dε/R - dr/R,  ΔP = P ((4dε/R)2 + (dr/R)2)1/2.
The uncertainties are added quaratically.
ΔP = uncertainty in P

Problem 5:  (E)

Properties of diodes

Problem 6:  (E)

Read a log-log scale

gain G = kω-2, log(G) = log(k) - 2log(ω).
The slope on the log-log plot in the region ω > 2*105 is -2.

Problem 7:  (C)

Counting statistics

The Gaussian distribution:  The standard deviation of the Gaussian distribution is given by σ = Navg1/2.  The standard deviation σ is a measure of the width of the distribution.  Approximately 1/3 of the counts will lie outside the interval Navg - σ to Navg + σ.

Problem 8:  (C)

Cross section σ

small beam, big target:  (# of particles scattered per second
= [(# of beam particles)/s] * [(# of target particles)/area ] * σ
(# of target particles)/area = number per unit volume * thickness).
Also:  only one answer is dimensionless.

Problem 9:  (D)


Absorption of radiation is a random process.  When a photon travels through a material, we cannot predict exactly how far it will penetrate and at which depth it will be absorbed, we can only predict the probability that the photon will travel through a certain distance Δx of the material.
I(z)  = I0exp(-kz),  I(3d)  = I0exp(-3kd) =  I0exp(-kd)3 = (1/2)3 I0 = (1/8)I0.

Problem 10:  (B)

Dead time

If R is the rate of particles reaching the detector,  r is the measured count rate, and T is the dead time of the detector then r = R/(1 + RT).
Dead time