Question 1

Arsenic-doped silicon is

Accepted Answer

A) a material with holes as the dominant charge carrier. 
B) an n-type semiconductor. 
C) a p-type semiconductor. 
D) all of the above. 
E) none of the above. 
A) a material with holes as the dominant charge carrier. 
B) an n-type semiconductor. 
C) a p-type semiconductor. 
D) all of the above. 
E) none of the above.

Question 2

In its lowest quantum state, a diatomic quantum mechanical rotator has a rotational energy of

Accepted Answer

A) zero. 
B) 2h/πI. 
C) h/2πI. 
D) h/πI. 
E) none of the given answers 
A) zero. 
B) 2h/πI. 
C) h/2πI. 
D) h/πI. 
E) none of the given answers

Question 3

A light emitting diode emits light of approximate wavelength 670 nm. What is the band gap?

Accepted Answer

A) 1.86 eV 
B) 4.14 eV 
C) 1.80 eV 
D) 3.72 eV 
E) 2.70 eV 
A) 1.86 eV 
B) 4.14 eV 
C) 1.80 eV 
D) 3.72 eV 
E) 2.70 eV

Question 4

Estimate the rotational energy (in eV) for a diatomic hydrogen molecule in the L = 2 quantum state. (The equilibrium separation for the H2 molecule is 0.075 nm.)

Accepted Answer

A) 0.011 eV 
B) 0.022 eV 
C) 0.033 eV 
D) 0.044 eV 
E) 0.055 eV 
A) 0.011 eV 
B) 0.022 eV 
C) 0.033 eV 
D) 0.044 eV 
E) 0.055 eV

Question 5

In a good conductor, the highest energy band containing electrons is

Accepted Answer

A) only partially filled. 
B) completely filled. 
A) only partially filled. 
B) completely filled.

Question 6

In an insulator, the valence band is

Accepted Answer

A) half filled. 
B) more than half filled. 
C) less than half filled. 
D) separated from the conduction band by ~5 or more eV. 
E) separated from the conduction band by ~1 or less eV. 
A) half filled. 
B) more than half filled. 
C) less than half filled. 
D) separated from the conduction band by ~5 or more eV. 
E) separated from the conduction band by ~1 or less eV.

Question 7

A semiconductor can conduct electricity

Accepted Answer

A) only below room temperature. 
B) never. 
C) only very much above room temperature. 
D) at room temperature but conductivity increases with increasing temperature. 
E) at room temperature but conductivity decreases with increasing temperature. 
A) only below room temperature. 
B) never. 
C) only very much above room temperature. 
D) at room temperature but conductivity increases with increasing temperature. 
E) at room temperature but conductivity decreases with increasing temperature.

Question 8

A diatomic molecule is vibrating in the v = 1 quantum state with a frequency of 2.0 × 1013 Hz. What is the energy of vibration?

Accepted Answer

A) 0.041 eV 
B) 0.083 eV 
C) 0.12 eV 
D) 0.15 eV 
E) 0.17 eV 
A) 0.041 eV 
B) 0.083 eV 
C) 0.12 eV 
D) 0.15 eV 
E) 0.17 eV

Question 9

When a voltage is applied across a p-type semiconductor, the holes

Accepted Answer

A) are increased in number. 
B) are destroyed. 
C) move toward the positive electrode. 
D) move toward the negative electrode. 
E) do not move. 
A) are increased in number. 
B) are destroyed. 
C) move toward the positive electrode. 
D) move toward the negative electrode. 
E) do not move.

Question 10

A simple junction transistor consists of three semiconductor sections consisting of

Accepted Answer

A) pnp semiconductors. 
B) npn semiconductors. 
C) either pnp or npn semiconductors. 
D) none of the given answers 
A) pnp semiconductors. 
B) npn semiconductors. 
C) either pnp or npn semiconductors. 
D) none of the given answers

Question 11

At room temperature (~295 K with kT ~ 0.025 eV), what fraction of the free electrons in a semiconductor with an energy gap of 1.5 eV can be expected to be in the conduction band?

Accepted Answer

A) 10-9 
B) 10-13 
C) 10-30 
D) 0.03 
E) 10-15 
A) 10-9 
B) 10-13 
C) 10-30 
D) 0.03 
E) 10-15

Question 12

Suppose the first excited vibrational state of a molecule is at 1.50 eV. If the potential is close to that of a simple harmonic oscillator, the energy of the ground state is

Accepted Answer

A) 0 eV 
B) 0.25 eV 
C) 0.30 eV 
D) 0.50 eV 
E) 0.75 eV 
A) 0 eV 
B) 0.25 eV 
C) 0.30 eV 
D) 0.50 eV 
E) 0.75 eV

Question 13

The ionic bond forms because the atoms involved

Accepted Answer

A) are naturally ions. 
B) have spherically symmetric charge distributions. 
C) are the same. 
D) all of the above 
E) none of the above 
A) are naturally ions. 
B) have spherically symmetric charge distributions. 
C) are the same. 
D) all of the above 
E) none of the above

Question 14

The characteristic rotational energy, h2/8π2I, for O2 is 2.9 × 10-23 J. Calculate the O2 bond length.

Accepted Answer

A) 3.6 × 10-10 m 
B) 0.60 × 10-11 m 
C) 1.2 × 10-10 m 
D) 0.30 × 10-11 m 
E) 2.4 × 10-10 m 
A) 3.6 × 10-10 m 
B) 0.60 × 10-11 m 
C) 1.2 × 10-10 m 
D) 0.30 × 10-11 m 
E) 2.4 × 10-10 m

Question 15

The energy gap between the valence and conduction bands in a certain semiconductor is 1.25 eV. What is the threshold wavelength for optical absorption in this substance?

Accepted Answer

A) 599 nm 
B) 639 nm 
C) 959 nm 
D) 873 nm 
E) 995 nm 
A) 599 nm 
B) 639 nm 
C) 959 nm 
D) 873 nm 
E) 995 nm

Question 16

Metallic bonding is caused by

Accepted Answer

A) the sharing of electrons by all atoms. 
B) the transfer of electrons between atoms. 
C) unequal charge distributions around neutral molecules. 
D) atoms bonding to hydrogen molecules. 
E) atoms bonding to oxygen molecules. 
A) the sharing of electrons by all atoms. 
B) the transfer of electrons between atoms. 
C) unequal charge distributions around neutral molecules. 
D) atoms bonding to hydrogen molecules. 
E) atoms bonding to oxygen molecules.

Question 17

The binding energy of a molecule

Accepted Answer

A) is the negative of the activation energy. 
B) cannot be negative if a molecule is formed. 
C) must be negative if a molecule is formed. 
D) can be negative if a molecule is formed. 
E) must be positive if the molecule is formed. 
A) is the negative of the activation energy. 
B) cannot be negative if a molecule is formed. 
C) must be negative if a molecule is formed. 
D) can be negative if a molecule is formed. 
E) must be positive if the molecule is formed.

Question 18

A material has an energy gap of 2.5 eV. What energy photons in the visible range (1.8 eV to 3.6 eV) would excite electrons into the conduction band?

Accepted Answer

A) 1.8 eV 
B) 2.5 eV 
C) 1.8 eV up to 2.5 eV 
D) 2.5 eV up to 3.6 eV 
E) 1.5 eV 
A) 1.8 eV 
B) 2.5 eV 
C) 1.8 eV up to 2.5 eV 
D) 2.5 eV up to 3.6 eV 
E) 1.5 eV

Question 19

In its lowest quantum state, the energy of a diatomic harmonic oscillator is

Accepted Answer

A) (1/4)hf. 
B) (1/2)hf. 
C) hf. 
D) 2hf. 
E) (3/2)hf. 
A) (1/4)hf. 
B) (1/2)hf. 
C) hf. 
D) 2hf. 
E) (3/2)hf.

Question 20

If a metal had a Fermi level of 5.0 eV, what would be the average energy of the electrons at 0 K?

Accepted Answer

A) 8.0 eV 
B) 6.0 eV 
C) 3.0 eV 
D) 0 
E) 5.0 eV 
A) 8.0 eV 
B) 6.0 eV 
C) 3.0 eV 
D) 0 
E) 5.0 eV

Exam 40: Molecules and Solids

Arsenic-doped silicon is

In its lowest quantum state, a diatomic quantum mechanical rotator has a rotational energy of

A light emitting diode emits light of approximate wavelength 670 nm. What is the band gap?

Estimate the rotational energy (in eV) for a diatomic hydrogen molecule in the L = 2 quantum state. (The equilibrium separation for the H2 molecule is 0.075 nm.)

In a good conductor, the highest energy band containing electrons is

In an insulator, the valence band is

A semiconductor can conduct electricity

A diatomic molecule is vibrating in the v = 1 quantum state with a frequency of 2.0 × 1013 Hz. What is the energy of vibration?

When a voltage is applied across a p-type semiconductor, the holes

A simple junction transistor consists of three semiconductor sections consisting of

At room temperature (~295 K with kT ~ 0.025 eV), what fraction of the free electrons in a semiconductor with an energy gap of 1.5 eV can be expected to be in the conduction band?

Suppose the first excited vibrational state of a molecule is at 1.50 eV. If the potential is close to that of a simple harmonic oscillator, the energy of the ground state is

The ionic bond forms because the atoms involved

The characteristic rotational energy, h2/8π2I, for O2 is 2.9 × 10-23 J. Calculate the O2 bond length.

The energy gap between the valence and conduction bands in a certain semiconductor is 1.25 eV. What is the threshold wavelength for optical absorption in this substance?

Metallic bonding is caused by

The binding energy of a molecule

A material has an energy gap of 2.5 eV. What energy photons in the visible range (1.8 eV to 3.6 eV) would excite electrons into the conduction band?

In its lowest quantum state, the energy of a diatomic harmonic oscillator is

If a metal had a Fermi level of 5.0 eV, what would be the average energy of the electrons at 0 K?

Introduction, Measurement, Estimating

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Filters

Estimate the rotational energy (in eV) for a diatomic hydrogen molecule in the L = 2 quantum state. (The equilibrium separation for the H₂ molecule is 0.075 nm.)

A diatomic molecule is vibrating in the v = 1 quantum state with a frequency of 2.0 × 10¹³ Hz. What is the energy of vibration?

The characteristic rotational energy, h²/8π²I, for O₂ is 2.9 × 10^-²³ J. Calculate the O₂ bond length.