My Professor gave us 10 Chapters of Physics homework to do in a week! While I have gotten most of it done, there are a few questions I was unable to find answers to. Is there any way you can help me out a little bit?
When an electron in an atom makes a transition from an excited energy level to its ground state, it emits a photon with an energy of 5 eV. (an eV or electron-Volt is a unit of energy). How much energy is required to cause the electron to transition from the ground state back up to the same excited energy level?
(a) 1 eV (b) 2.5 eV (c) 5 eV (d) 10 eV (e) Cannot be determined from the info given
A recent European study found no link between long term heavy cell phone use and cancer despite the fact that cell phones are emitting electromagnetic radiation (microwaves) when held next to our ears. Too much exposure to X-rays is clearly linked to cancer. Why the difference?
(a) Microwaves have shorter wavelengths than X-rays, so they pass through our bodies without interacting
(b) X-rays travel at higher speeds than microwaves so they collide with more atoms per second and have more potential to do damage
(c) Cell phone companies pay for most scientific research in Europe
(d) Microwave photons have less energy than X-ray photons so they cannot knock electrons out of atoms
(e) X-rays are charged particles and can do more damage than the uncharged photons in microwaves
Why is the sky blue?
(a) Radioactive decays within the nucleus of nitrogen atoms emit blue light
(b) Protons in the gas molecules that transition between energy levels that correspond to blue light
(c) Electrons in the gas molecules that transition between discrete energy levels that correspond to blue light
(d) Angular momentum of the gas molecules with a frequency that corresponds to blue light
(e) Blackbody radiation from the upper atmosphere that is strongest in the blue part of the spectrum
Quantum mechanics tells us that the properties and behavior of atoms and molecules are random and subject to the laws of probability. What does this mean about macroscopic measurements like the pressure and temperature of a gas?
(a) The temperature and pressure of the gas are also random measurements
(b) There is very low probability of actually measuring the pressure and temperature of the gas
(c) Quantum mechanics does not apply to macroscopic systems
(d) Pressure and temperature are bulk properties, so they have nothing to do with the motion of atoms and molecules
(e) The temperature and pressure of the gas are not random because they are the average of a very large number of random interactions
Which of the following statements is true about the inner shell electrons in a gold atom (atomic number 79) and a titanium atom (atomic number 22)?
(a) The inner electrons in titanium are closer to the nucleus on average than those in gold
(b) The inner electrons in gold are closer to the nucleus on average than those in titanium
(c) The inner electrons in titanium are at the same average distance from the nucleus as those in gold
(d) There is no way to predict the average distance from the nucleus to the inner electrons
An American 60 Watt light bulb is designed to operate at 110 Volts. A European 60 Watt light bulb is designed to operate at 220 Volts. Which bulb has the higher resistance?
(a) The American bulb (b) The European bulb (c) Both have the same resistance
Electrons are held in atoms by:
(a) The gravitational force
(b) The electric force
(c) The strong nuclear force
(d) The weak nuclear force
(e) Atomic gnomes
A generator uses magnetic induction to:
(a) Convert mechanical energy into heat
(b) Convert heat into mechanical energy
(c) Convert mechanical energy into electrical energy
(d) Convert electrical energy into current
(e) Convert electric current into voltage
A light bulb is connected to the terminals of the battery and the light glows. Which statement is true?
(a) The wires carry electric current because the wires have more electrons than protons
(b) More current leaves the battery than enters the battery
(c) Less current enters the light bulb than leaves the light bulb
(d) The light bulb filament does not acquire an electric charge
(e) The current decreases steadily as it flows around the circuit
A quantum of light is called a
(a) Proton (b) Neutron (c) Electron (d) Fermion (e) Photon
According to the uncertainty principle:
(a) It is impossible to measure the energy of a subatomic particle.
(b) If we measure an electron’s speed more precisely, we can determine its position more precisely.
(c) If we measure an electron’s speed more precisely, we can determine its position less precisely.
(d) The entropy or disorder of the universe is constant.
Different isotopes of the same element have different numbers of:
(a) Neutrons (b) Protons (c) Electrons (d) Photons (e) Neutrinos
When you comb your hair, the hair becomes positively charged. What else becomes charged?
(a) Your head becomes negatively charged
(b) The comb becomes negatively charged
(c) The comb becomes positively charged
(d) Your head becomes positively charged
(e) Nothing. Only your hair is charged.
Which is true about a transformer?
(a) A transformer can operate more efficiently on DC input than AC
(b) A transformer requires a strong permanent magnet
(c) The output voltage is always lower than the input voltage because of energy loss
(d) A transformer only works for AC input
(e) A transformer only works for DC input
There are countless freely moving electrons in a penny, and they all repel each other. Why don’t they fly out of the penny?
(a) They are attracted to the equally countless number of protons in the penny.
(b) The repulsive electrical force is balanced by an attractive gravitational force between the electrons
(c) Electrons are not permitted to be outside atoms due to the quantum uncertainty principle
(d) There is a magnetic field on the surface of the penny that effectively confines them
(e) The penny is electrically insulated
A negatively charged metal sphere in a vacuum chamber is exposed to UV light which causes the sphere to lose its charge and end up with zero charge. What will happen when the same sphere is positively charged and then exposed to the same UV light?
(a) It will lose its charge and end up with zero charge
(b) It will gain more positive charge
(c) It will lose its charge, and acquire a negative charge
(d) It will not gain or lose charge
How did Rutherford’s experiment of scattering alpha particles from gold foil indicate that there was a very small and very massive nucleus in the gold atoms?
A small but strong magnet will fall through a vertical metal tube very slowly, but a non-magnetic object of the same size and mass falls quickly. Why does the magnet fall so slowly?
Considering the falling magnet in question 64, identify the work being done and the energy changes as the magnet falls at constant speed. Be sure to identify where energy is coming from or going to.
Why do more cosmic rays strike Canada than Mexico?
Pick any method of electrical power generation and describe how it works. Where does the energy come from? Don’t just name the fuel or energy source, but identify the physical processes that release or transfer the energy from the source to the electric current.
I counted over 20 questions. That is a lot more than "a few". Many are easy multiple choice questions for which you should have some idea of the answer if you expect to pass the course, or have learned any physics at all.
Someone will be glad to critique your efforts.
None of the choices of "why is the sky blue" is correct, by the way. Your "professor" should know that. Isn't "none of the above" an option?
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Yes, I can help you with these questions!
Let's start with question 1:
To determine the amount of energy required to cause the electron to transition from the ground state back up to the same excited energy level, we need to understand that the emission and absorption of photons corresponds to the energy difference between the two energy levels involved.
In this case, the electron emitted a photon with an energy of 5 eV when transitioning from the excited energy level to the ground state. This means that the energy required to cause the electron to transition back up to the excited energy level would be the same.
Therefore, the answer to this question is (c) 5 eV.
Now, let's move to question 2:
The question asks why there is a difference in the effect of long-term heavy cell phone use and X-ray exposure on cancer risk.
The correct answer is (d) Microwave photons have less energy than X-ray photons so they cannot knock electrons out of atoms.
Microwaves emitted by cell phones have lower energy than X-rays. X-rays have higher energy and, therefore, have more potential to interact with atoms and knock electrons out of them, which can cause damage to cells and potentially lead to cancer. In contrast, the lower energy of microwaves makes it less likely for them to have such interactions and cause the same level of damage.
Moving on to question 3:
The question asks why the sky is blue.
The correct answer is (c) Electrons in the gas molecules that transition between discrete energy levels that correspond to blue light.
The blue color of the sky is due to the scattering of sunlight by the Earth's atmosphere. The gas molecules in the atmosphere, particularly nitrogen and oxygen, absorb and re-emit electromagnetic radiation at various wavelengths. When sunlight (which consists of a range of wavelengths) interacts with these gas molecules, the shorter blue wavelengths are scattered more efficiently than the longer wavelengths. This scattering of blue light is what gives the sky its blue color.
Next, let's tackle question 4:
The question relates to the randomness and probability associated with quantum mechanics and its implications for macroscopic measurements like pressure and temperature of a gas.
The correct answer is (e) The temperature and pressure of the gas are not random because they are the average of a very large number of random interactions.
In quantum mechanics, the behavior of individual atoms and molecules is described by probability distributions. However, when dealing with a large number of particles (such as in a gas), the statistical behavior of these particles averages out, leading to well-defined properties like temperature and pressure. Although the underlying atomic and molecular processes are probabilistic, the macroscopic measurements of temperature and pressure represent the collective behavior and are not random themselves.
Now, let's move to question 5:
This question compares the average distance of inner shell electrons from the nucleus in a gold atom (atomic number 79) and a titanium atom (atomic number 22).
The correct answer is (a) The inner electrons in titanium are closer to the nucleus on average than those in gold.
The average distance of inner shell electrons from the nucleus generally decreases as the atomic number increases. Titanium (atomic number 22) has a smaller atomic number compared to gold (atomic number 79), suggesting that the inner electrons in titanium are closer to the nucleus on average than those in gold.
Let's proceed to question 6:
This question asks which bulb, between an American 60 Watt light bulb designed to operate at 110 Volts and a European 60 Watt light bulb designed to operate at 220 Volts, has the higher resistance.
The correct answer is (a) The American bulb.
Resistance in a circuit depends on the voltage and wattage. In this case, both bulbs have the same wattage (60 Watts), but the American bulb is designed to operate at 110 Volts while the European bulb is designed to operate at 220 Volts. Using Ohm's law (V = IR), we can see that a higher voltage with the same wattage results in a lower resistance. Therefore, the American bulb has the higher resistance.
Moving on to question 7:
The question asks what holds electrons in atoms.
The correct answer is (b) The electric force.
Electrons are held in atoms by the electric force of attraction between the negatively charged electrons and the positively charged nucleus. The electric force allows the electron to remain in an orbit around the nucleus, creating a stable atom.
Next, let's tackle question 8:
This question relates to the purpose of a generator and how it works.
The correct answer is (c) Convert mechanical energy into electrical energy.
A generator uses magnetic induction to convert mechanical energy (such as that provided by a turbine) into electrical energy. Inside a generator, a magnet is rotated within a coil of wire, which induces a current in the wire. This current is what we refer to as electrical energy, which can be used to power various devices.
Now, let's move to question 9:
This question asks about the nature of electric current in a circuit with a light bulb connected to a battery.
The correct answer is (c) Less current enters the light bulb than leaves the light bulb.
In a closed circuit, the amount of current entering a component (like a light bulb) is equal to the amount of current leaving that component. The light bulb acts as a resistance in the circuit, causing a decrease in the flow of current. Therefore, less current enters the light bulb than leaves it.
Finally, let's answer question 10:
This question asks about the quantum of light, which is commonly known as a photon.
The correct answer is (e) Photon.
A quantum of light is called a photon. Photons are the smallest bundles or packets of electromagnetic energy, and they behave both as particles and waves.
I hope this helps! Let me know if you have any further questions.