Nuclear & Particle Physics - Standard Model

According to the Standard Model of elementary particles, which of the following is NOT a composite object?

A. Muon
B. Pi-meson
C. Neutron
D. Deuteron
E. Alpha particle

(GR9677 #63)

Solution:

A.TRUE
Muon is a lepton. Leptons, along with quarks, are considered the fundamental particles.

B. FALSE
Pi-Meson consists of a quark and its antiparticle. Moreover, a pi-meson is a hadron. Hadrons interact with the strong-force, and all of them are composed of combinations of quarks. (The fundamental particles are classified as quarks and leptons.)

C. FALSE
A neutron is made up of 3 quarks.

D. FALSE
A deuteron consists of a proton and a neutron. (tritium is two neutrons and a proton, while regular Hydrogen is just an electron and proton).

E. FALSE
An alpha particle consists of electrons and protons and neutrons.

Answer: A

Thermal Physics - Probability

Which of the following is true if the arrangement of an isolated thermodynamic system is of maximal probability?

A. Spontaneous change to a lower probability occurs
B. The entropy is minimum
C. Botzmann’s constant approaches zero
D. No spontaneous change occurs
E. The entropy is zero

(GR9277 #63)

Solution:

Maximal Probability → highest/maximum entropy → most stable state /equilibrium → No spontaneous change occurs. Spontaneous change occurs when the system is far from equilibrium.

Answer: D

Nuclear & Particle Physics - EM Spectrum

Electromagnetic radiation provides a means to probe aspects of the physical universe. Which of the following statements regarding radiation spectra is NOT correct?

1. Lines in the infrared, visible, and ultraviolet regions of the spectrum reveal primarily the nuclear structure of the sample.
2. The wavelengths identified in an absorption spectrum of an element are among those in its emission spectrum.
3. Absorption spectra can be used to determine which elements are present in distant stars.
4. Spectral analysis can be used to identify the composition of galactic dust.
5. Band spectra are due to molecules.

(GR0177 #64)

Solution:

The EM spectrum of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.

 EM spectrum can be used to determine the elements that compose the object, not the nuclear structure. (A) FALSE

Answer: A