MIDTERM 3 REVIEW SESSION Dr. Flera Rizatdinova

Summary of Chapter 23

•  Index of refraction:

•  Angle of reflection equals angle of incidence

•  Plane mirror: image is virtual, upright, and the same size as the object

•  Spherical mirror can be concave or convex

•  Focal length of the mirror:

Summary of Chapter 23

•  Mirror equation:

•  Magnification:

•  Real image: light passes through it

•  Virtual image: light does not pass through

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Summary of Chapter 23

  Law of refraction (Snell’s law):

  Total internal reflection occurs when angle of incidence is greater than critical angle:

  A converging lens focuses incoming parallel rays to a point

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Summary of Chapter 23

•  A diverging lens spreads incoming rays so that they appear to come from a point

•  Power of a lens:

•  Thin lens equation:

•  Magnification: © 2014 Pearson Education, Inc.

Summary of Chapter 24

•  Wavelength of light in a medium with index of refraction n:

•  In the double-slit experiment, constructive interference occurs when

•  and destructive interference when

•  Two sources of light are coherent if they have the same frequency and maintain the same phase relationship

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Summary of Chapter 24

•  Light bends around obstacles and openings in its path, yielding diffraction patterns

•  Light passing through a narrow slit will produce a central bright maximum of width

•  Interference can occur between reflections from the front and back surfaces of a thin film

•  Light whose electric fields are all in the same plane is called plane polarized

•  The intensity of plane polarized light is reduced after it passes through another polarizer:

Summary of Chapter 25

•  Simple magnifier: object at focal point

•  Angular modification:

•  Astronomical telescope: objective and eyepiece; object infinitely far away

•  Magnification:

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Problems

  A beam of light in water (of refractive index of 1.33) enters a glass slab (of refractive index 1.50) at an angle of incidence of 60.0°. What is the angle of refraction in the glass?

  Answer: 50.2°

  Light passes through three ideal polarizing sheets. Unpolarized light enters the first sheet and the resultant vertically polarized beam continues through the second sheet and third sheet. The second sheet has its transmission axis at 50° with respect to the first sheet, and the third sheet is at 70° with respect to the first sheet.   (a) What percent of the original intensity emerges from filter #1?   (b) What percent of the original intensity emerges from filter #2?   (c) What percent of the original intensity emerges from filter #3?

  Answer: (a) 50% (b) 21% (c) 18%

Summary of Chapter 27

•  Planck’s hypothesis: molecular oscillation energies are quantized

•  Light can be considered to consist of photons, each of energy

•  Photoelectric effect: incident photons knock electrons out of material •  An increase in intensity of the light beam results in the larger rate of ejected

electrons, but the maximum kinetic energy of electrons is not changed by an increase in intensity

•  If the frequency of the light is increased, the maximum kinetic energy of the electrons increases linearly

•  If the frequency is less that the “cutoff” frequency, no electrons will be ejected, no matter how great is the intensity of the light.

Summary of Chapter 27

•  Compton effect and pair production also support photon theory

•  Wave-particle duality—both light and matter have both wave and particle properties

•  Wavelength of an object with mass:

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Summary of Chapter 28

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•  Quantum mechanics is the basic theory at the atomic level; it is statistical rather than deterministic

•  Heisenberg uncertainty principle:

•  Electron state in atom is specified by four numbers, n, l, ml, and ms

Summary of Chapter 28

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•  n, the principal quantum number, can have any integer value, and gives the energy of the level

•  l, the orbital quantum number, can have values from 0 to n − 1

•  ml, the magnetic quantum number, can have values from −l to +l

•  ms, the spin quantum number, can be +½ or −½

Summary of Chapter 30

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•  Nuclei contain protons and neutrons—nucleons

•  Total number of nucleons, A, is atomic mass number

•  Number of protons, Z, is atomic number

•  Isotope notation:

•  Nuclear masses are measured in u; carbon-12 is defined as having a mass of 12 u

1 u = 1.6605 × 10−27 kg = 931.5 MeV/c2

Summary of Chapter 30

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•  Difference between mass of nucleus and mass of its constituents is binding energy

•  Unstable nuclei decay through alpha, beta, or gamma emission

•  An alpha particle is a helium nucleus; a beta particle is an electron or positron; a gamma ray is a highly energetic photon

•  Nuclei are held together by the strong nuclear force; the weak nuclear force is responsible for beta decay

Summary of Chapter 30

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•  Electric charge, linear and angular momentum, mass-energy, and nucleon number are all conserved

•  Radioactive decay is a statistical process

•  The number of decays per unit time is proportional to the number of nuclei present:

•  The half-life is the time it takes for half the nuclei to decay

Problems

  Calculate the de Broglie wavelength of an electron if it is accelerated from rest by 500 V.

  Solution: The final KE of the electron equals the negative change in its PE as it passes through the potential difference.

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KE = −qV ⇒12mv 2 = −eV ⇒ v =

−2eVm

v =1.6 ×10−19C⋅ 911V9.11×10−31kg

=1.26 ×107m / s

p = mv =1.15 ×10−24 kg⋅ m / s

λ =hp

=6.63 ×10−34 kg⋅ m2 / s1.15 ×10−24 kg⋅ m / s

= 0.576 nm

Problems

  If the maximum possible accuracy in measuring the velocity of a particle increases, the maximum possible accuracy in measuring its position will   A) increase.

  B) decrease.   C) not be affected.

  Answer: B

Problems

  The symbol for a certain isotope of polonium is . How many neutrons are there in the nucleus of this isotope?

  A) 84   B) 130   C) 214   D) 298   E) 314   Answer: B

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84214Po

Problems

  A radioactive isotope of atomic number Z emits a beta-minus particle, and then the daughter nucleus emits a gamma ray. What is the atomic number of the resulting nucleus after both processes?