# Physics Principles and Problems 2009

## Chapter 27: Quantum Theory

### Standardized Test Practice

1
The illustration below shows electron emission after light strikes the cathode of a photocell. If the stopping potential of the photocell is 3.7 V, what kinetic energy is given to the electrons?

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A)7.3 × 10–16 J
B)5.9 × 10–19 J
C)6.4 × 10–21 J
D)4.8 × 10–22 J
2
The light that strikes the cathode has a frequency of 6.4 × 1014 Hz. What is the energy of a photon at this frequency?

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A)2.1 eV
B)2.6 eV
C)3.4 eV
D)5.8 eV
3
A piece of cobalt has a work function of 5.0 eV. What is this piece's threshold wavelength?
A)248 nm
B)387 nm
C)434 nm
D)620 nm
4
Which of the following best describes the nature of light?
A)Light has wave properties only.
B)Light has particle properties only.
C)Light has neither wave nor particle properties.
D)Light has both wave and particle properties.
5
Light from a mercury vapor lamp (λ = 254 nm) strikes a sample of rubidium. The rubidium has a work function of 2.16 eV. What is the kinetic energy of the electrons ejected from the sample?
A)1.90 eV
B)2.26 eV
C)2.72 eV
D)4.88 eV
6
The illustration shows two metal plates with a potential difference of 87 V between them. An electron is accelerated from rest from the cathode to the anode. What is the speed of the electron when it reaches the anode?

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 Need a Hint?
A)1.4 × 106 m/s
B)2.3 × 106 m/s
C)3.9 × 106 m/s
D)5.5 × 106 m/s
7
An electron has a velocity of 9.3 × 105 m/s. What is its de Broglie wavelength?
A)0.49 nm
B)0.78 nm
C)0.88 nm
D)1.3 nm
8
A positron has a de Broglie wavelength of 2.07 nm. What is its kinetic energy? (A positron is a particle with the mass of an electron and the charge of a proton.)
 Need a Hint?
A)0.300 eV
B)0.351 eV
C)0.599 eV
D)0.702 eV
9
You cannot observe the wave nature of everyday objects. How did de Broglie account for this in his model?
 Need a Hint?
A)In de Broglie's model, the wavelengths of everyday objects are too short to produce observable effects.
B)According to de Broglie's model, the Heisenberg uncertainty principle prevents the accurate measurement of de Broglie wavelengths.
C)In de Broglie's model, the wavelengths of everyday objects are too long to produce observable effects.
D)In de Broglie's model, only sub-atomic particles have a wave nature.
10
What did scientists observe that led them to accept de Broglie's proposals about the wave properties of particles?
A)Scientists observed the photoelectric effect and Compton scattering.
B)Scientists observed electrons being ejected from a graphite block.
C)Scientists observed that only very small particles exhibit wave properties.
D)Scientists observed the diffraction patterns of electrons.