Physics 10 Review
Hammering or heating a permanent magnet can demagnetize it. What happens to the magnetic domains inside it during these processes?
The magnetic domains will lose their uniform orientations and become more randomly oriented
You are on a bullet train that consists of three cars. Using your physics 10 knowledge, you decide to analyze the net force on each car when you are traveling at a constant velocity. After some thought, you are able to conclude that the net force on (a) the front car, b) the middle car, and (c) the back car is A) (a)backward; (b) zero; (c) forward B) (a)forward; (b)zero; (c) backward C) (a)zero; (b)zero; (c)zero D) (a)forward; (b)forward; (c) forward E) dependent on whether the train is going slow or fast
C) (a)zero; (b)zero; (c)zero
Anthony Davis made buzzer- beater-3-point shot to win crucial game 2 of the Western Conference finals a couple weeks ago. After the ball left his hands, did a horizontal force keep the ball moving forward in order for the ball to reach the basket? If so, what is the force? A) Yes, there is a horizontal force. Inertia B) Yes, there is a horizontal force. Gravity C) No, there is no horizontal force. D) Yes, there is a horizontal force. The horizontal force is supplied by Anthony's hand. E) None of the above
C) No, there is no horizontal force.
What is the main reason a DVD can hold more information than a CD, aside from the number of layers of data storage medium?
DVD's use shorter-wavelength light than CD's.
f the low-pressure neon gas in a neon sign were replaced by a low-pressure mercury gas, the sign would emit almost no visible light. Why not?
Excited mercury atoms emit primarily invisible ultraviolet light.
A xerographic copier uses a special photoconductor surface that allows light from an original document to control the placement of black powder on white paper. The photoconductor only conducts electricity when it's exposed to light because in the dark,
electrons in the photoconductor completely fill its valence levels and can't shift from one level to another in order to transport charge through the material.
If you bring a button magnet near a steel pipe, they will soon begin attracting one another. Why don't they repel?
The button magnet's magnetic field polarizes the steel pipe and the pipe develops an opposite pole near the approaching pole of the button magnet and thus attract the magnet.
Many sophisticated cameras have zoom lenses. When you select the telephoto setting, the objects in front of you appear much closer. In this setting,
the focal length of the lens is longer than normal.
A typical bar magnet sometimes has one side painted red on its north pile end and one side painted on its south pole end. With the right tools, you might be able to change this bar magnet in one or more of the following ways: (1) remove its magnetic poles altogether (2) reverse its magnetic poles so that it has a North at the white end and a South at the red end (3) convert its north pole into a south pole so that it has south poles at both ends and no north poles. Which of those three options is physically possible?
(1) remove its magnetic poles altogether (2) reverse its magnetic poles so that it has a North at the white end and a South at the red end
To read the magnetic strip on an ID or credit card, you must swipe it quickly past a tiny coil of wire. Why must the card be moving for the coil system to read it?
A moving magnet will induce a current in the coil so that the magnetic strip can be read
Why are microwave TV dinners typically packaged in plastic rather than aluminum trays?
Aluminum trays would reflect the microwaves which would result in improperly cooked food
If electrons had four different internal states that could be distinguished from one another, how many electrons could occupy the same orbital without violating the Pauli exclusion principle?
Any number from 0 to 4 electrons
One type of microphone has a permanent magnet and coil of wire that move relative to one another in response to sound waves. Why is the current in the coil related to motion?
As a coil moves through the magnetic field, electric charges in the coil experience forces and thus flow through the coil as current that is proportional to the coil's velocity through the magnetic field
You have two button magnets that you pull apart, each which has a north and a south pole. The magneto-static forces between two button magnets decrease surprisingly quickly as their separation increases. Consider Columb's Law for magnetism and the dipole character of each button magnet to explain this effect.
As separation distance increases, the distance separating the pair of poles in each of the button magnets is very small compared to the separation of the two button magnets, and therefore the attractive and repulsive forces nearly cancel.
Most commercial airliners have static dissipaters on their wingtips. These sharp metal spikes extend from the end of each metal wing and point toward the rear of the plane. Suppose a plane had just flown through a negatively charged cloud and acquired a large negative charge. It is not flying through neutral air. Which of the following should you expect to happen near static dissapaters? A) a corona discharge at the dissipater tips will spray positive charge into the air B) Any charge on the dissipaters will flow towards the wings, leaving the dissapaters neutral C) A corona discharge at the dissipater tips will spray negative charge into the air D) Nothing, because the air is neutral E) the charge will remain on the wings since charge is a conserved quantity
C) A corona discharge at the dissipater tips will spray negative charge into the air
Holding your hand on a static generator (e.g. a Van de Graff generator) can make your hair stand up, but only if you are standing on a good electrical insulator. Why is that insulator important? A) it is not, standing on an insulator or a conductor will have the same end results B) it is not, standing on a conductor would be better than an insulator since charges flow readily through a conductor. C) Standing on an insulator allows you to retain the charges transferred from the static generator. D) Standing on an insulator prevents you from retaining the charges transferred from the static generator,
C) Standing on an insulator allows you to retain the charges transferred from the static generator.
When the brakes on his big rig truck fail, the driver steers it up a runaway truck ramp. As the truck rolls up the ramp, it slows to a stop. What happens to the truck's kinetic energy, its energy of motion? A) it is lost B) it turns into heat C) it converts into gravitational potential energy D) it turns into friction E) it increases
C) it converts into gravitational potential energy
An African butterfly fish can jump above the freshwater's surface. Why doesn't gravity prevent them from leaving the water? A) the water pushes the African butterfly fish out B) the surface water breaks the pull of gravity C) the African butterfly fish has inertia as it approaches the surface D) the African butterfly fish is being pushed out of the water by another fish E) Gravity has no effect on the water
C) the African butterfly fish has inertia as it approaches the surface
A baseball contains an enormous number of electrically charged particles. Why don't two baseballs normally exert electrostatic forces on each other? A) their mass is too small to exert electrostatic forces B) the electrostatic forces cancel due to like net charges on each ball C) the electrostatic forces cancel due to zero net charges on each ball D)the electrostatic forces cancel due to opposite net charges on each ball E) They exert electrostatic forces, but they not observed since the electric force is small
C) the electrostatic forces cancel due to zero net charges on each ball
Why is it important that the filament of a light bulb have a much larger electrical resistance that the supporting wires that carry current to and from that filament? A) a larger electrical resistance has a smaller voltage drop and thus consumes less electrical power B) a larger electrical resistance has a larger voltage drop and thus consumes less electrical power C)a larger electrical resistance has a larger voltage drop and thus consumes more electrical power D) a larger electrical resistance has a smaller voltage drop and thus consumes more electrical power E) a larger electrical resistance extends the lifetime of the bulb
C)a larger electrical resistance has a larger voltage drop and thus consumes more electrical power
Your cute bunny has lept out of her cage and has chewed the cord to your desk lamp, which has created a short circuit an electric connection from one wire to the other inside the cord. When you plug the lamp into the electrical outlet, A) current will flow alternately through the bulb and throughout the short circuit B) excessive current will pass through the bulb C)current will bypass the bulb D) the bulb will blink on and off rapidly E) the bulb will glow very brightly F) the bulb will not light up
C)current will bypass the bulb F) the bulb will not light up
If most of the highest energy valence levels in a diode laser's p-type anode weren't empty, it would become relatively inefficient and probably wouldn't emit laser light at all. Why not?
Electrons in the highest valence levels can absorb the laser light while undergoing radiative transitions to the conduction levels and that absorption would trap the laser radiation and reduce the diode's ability to emit laser light.
Thermal energy can shift some of the electrons in a hot semiconductor from valence levels to conduction levels. What effect do these shifts have on the semiconductor s ability to conduct electricity?
Semiconductor's ability to conduct electricity increases
Some makeup mirrors allow users to choose either fluorescent or incandescent illumination to match the lighting in which they'll be seen. Why does the type of illumination affect their appearances?
Since incandescent light has less blue than fluorescent light, incandescent light reflected from a person's skin would also have less blue in it. Since incandescent light has more red than fluorescent light, incandescent light reflected from a person's skin would also have more red in it. Since incandescent light has more red than fluorescent light, incandescent light reflected from a person's skin would have less blue in it.
Increasing the power delivered to an incandescent bulb makes its filament hotter and its light whiter. Why doesn't increasing the power to a neon sign change its color?
The incandescent lamp is emitting thermal radiation with a roughly black body spectrum. The neon sign is not a thermal light source, so increasing the power simply brightens its light but does not change its spectrum.
Do more magnetic flux lines begin or end on a button magnet, or are those numbers equal?
The magnetic flux lines beginning and ending on a button magnet are equal
The discharges in a mixture of gases are more likely to emit a full white spectrum of light than a discharge in a single gas. Why?
The more different atoms and molecules present in a mixture of gases, the more variety there is in the possible radiative transitions and thus, the more likely that a full spectrum of white light will be emitted by the discharge.
Sports photographers often use a large aperture, long focal length lenses. What limitations do these lenses impose on the photographs?
Their depths of focus are relatively small.
Unglazed ceramics, which are porous, can absorb water and moisture. Why should they not be used in a microwave oven ?
Water molecules trapped in the ceramics would: 1. Absorb the energy from the electromagnetic waves 2.Turn and bump into one another over and over again because of the fluctuating electric field of the microwave 3.convert the energy of the microwaves into thermal energy AND the ceramic would become extremely hot so ALL OF THE ABOVE
Compare how potato cooks in a microwave oven with how it cooks in an ordinary oven
In a microwave oven, the potato's water absorbs microwaves and that microwave energy becomes thermal energy and the potato's temperature rises uniformly. In an ordinary oven. heat flows gradually into the potato through it's surface and it's temperature rises NON-uniformly with the middle of the potato last to be cooked
Some of the laser light striking a DVD's reflective layer hits the flat region around a pit and reflects back toward the photodiode. How does this reflected wave actually reduce the amount of light detected by the photodiode?
Waves reflected by the pits and flats undergo refraction. Waves reflected by the pits and flats undergo total internal reflection. Waves reflected by the pits and flats undergo constructive interference. (None of the above choices are correct.) ***
MOSFET doesn't change instantly from a perfect insulator to a perfect conductor as you vary the charge on its gate. With intermediate amounts of charge on its gate, the MOSFET acts as a resistor with a moderate electrical resistance. This flexibility allows the MOSFET to control the amount of current flowing in a circuit. Explain why a MOSFET becomes warm as it controls that current.
When current flows through a MOSFET, the MOSFET acts as a resistor which results in a voltage drop across the MOSFET and thus some of the current's energy is converted into thermal energy.
Explain the strategy of putting highly radioactive materials in a storage place for many years as a way to make them less hazardous. That wouldn't work for chemical poisons, so why does it work for radioactive materials?
With time, radioactive nuclei will exponentially decay and the materials become less and less hazardous
An extremely fast-moving charged particle traveling in a magnetic field can radiate X-rays, a phenomenon known as a synchrotron radiation. Why is the magnetic field essential to this emission?
Without the magnetic field, the charged particle would travel at a constant velocity and would not radiate electromagnetic waves because of its constant velocity
If you're taking a photographic portrait of a friend and want objects in the foreground and background to appear blurry, how should you adjust the camera's aperture and shutter speed?
You should use the largest available aperture and a short shutter speed.
You hear a report that an engineer has found an unusual electromagnetic wave. This wave consists only of an electric field, with no magnetic field accompanying it. This peaks your attention since you are in Physics 10 and you are certain that the engineer is mistaken because
an electromagnetic wave must have a magnetic field that changes with time to produce its electric field
Fission chain reactions in uranium are sustained by neutrons, each of which is released by one fission and may induce subsequent fission. Each fission also releases other particles, which include protons. However, proton-containing fission fragments are not as effective at causing subsequent fissions because they
are repelled as they try to approach other uranium nuclei.
When you drop the North pole of s permanent magnet onto an aluminum sheet, it falls sightly slower than normal. The magnet is being repelled by the aluminum because
current induced in the aluminum by the approaching north pole produces a repelling north pole on the aluminum's surface
Increasing the diameter of a camera lens, while keeping its focal length unchanged, does more than just brighten the image on the film so that you can use a shorter exposure. It also
decreases the depth of focus so that objects at different distances will no longer all be in focus at once.
While the clear sky is blue, clouds are white. This indicates that the water molecules in clouds:
form droplets that are comparable to or larger than the wavelengths of visible light.
In a typical laser, the right color of light bounces back and forth between two mirrors and
is amplified by the excited atoms in the laser medium.
Laser light exhibits much stronger interference effects than light from a flashlight. This is because
laser light is both coherent and monochromatic
A photoconductor's electrical properties go from insulating to conducting when it is exposed to light because,
light supplies the energy needed to move electrons from the valence band to the conduction band.
For a nuclear weapon to explode normally, the fissionable material in its core must be assembled very quickly. For technical reasons, a nuclear bomb developed by a terrorist group would probably not achieve such rapid assembly. As a result of its slow assembly, such a bomb would
overheat and push itself apart during the assembly, producing only a weak explosion.
When you drop a strong magnet through the center of a copper pipe, the magnet
slowly because of its motion causes currents to flow in the pipe and those currents repel the magnet
The electric field around an electrically charged comb diminishes with distance from the comb. Explain this decrease in the magnitude of the field. A) the electrostatic forces between the comb and a positive charge diminish with decreasing separation distance which results in a smaller electric field B)the electrostatic forces between the comb and a positive charge grow with decreasing separation distance which results in a smaller electric field C) the electrostatic forces between the comb and a positive charge grow with increasing separation distance which results in a smaller electric field D) the electrostatic forces between the comb and a positive charge diminish with increasing separation distance which results in a smaller electric field E) This is not correct, the force remains constant
the electrostatic forces between the comb and a positive charge diminish with increasing separation distance which results in a smaller electric field
When laser light reflects from a soap bubble, its photons can interfere with one another. In contrast, when sunlight reflects from a soap bubble, each photon can interfere only with itself. The reason for this difference is that
the photons in a laser beam are all part of a single wave, while those in sunlight are independent waves.
Why can light from a blue laser form a narrower beam waist than light from an infrared laser?
the size of the beam waist depends largely on the wavelength of the light and since blue light has a shorter wavelength than infrared light, blue light can form a narrow beam waist.
A glass fiber can act as a pipe for light-light that enters the fiber at its end follows the fiber almost indefinitely without escaping through the fiber's surface. The light follows the fiber because
whenever it tries to leave the glass at a shallow angle, it's perfectly reflected.
When you look into the front of a square glass vase filled with water, its sides appear to be mirrored. Why do the sides appear so shiny?
The light that you are seeing is experiencing total internal reflection.
After you extract two pieces of Scotch magic tape from a tape dispenser, those pieces will repel one another. Explain their repulsion. A) Each piece of tape will acquire like charges while being extracted from the tape dispenser B)Each piece of tape will acquire opposite charges while being extracted from the tape dispenser C) one piece of tape will have a greater net charge which would repel the other piece D) the adhesive tape is sticky so it would always attract E) The premise is wrong, the pieces of tape will not repel because they are electrically neutral
A) Each piece of tape will acquire like charges while being extracted from the tape dispenser
Your precious younger sister is really on a roll this morning. After several "good ones," she then says "OK so you're taking physics right?" Here's one: if the acceleration of gravity is 9.8 m/s^2 then why isn't everything accelerating? Being a dedicated student you give this response some real thought and come up with: A) Gravity is just part of the story and it is the total net external force that determines the acceleration B) Gravity acts only on things that are not touching the surface C)Most objects have too much inertia for us to see them accelerate under the influence of gravity D) All things really do accelerate but we accelerate with them so we can't tell E) Gravity only affects certain objects
A) Gravity is just part of the story and it is the total net external force that determines acceleration
The two prongs of a power cord are meant to carry current to and from a lamp. If you were to plug only one of the prongs into an outlet, the lamp wouldn't light at all. Why wouldn't it at least glow at half it's normal brightness? Which of the following are correct statements: A) No current flows B) Current flows C) An open circuit is created D) Charges in the lamp are destroyed E) A closed circuit is created
A) No current flows
Which of the following can cause a charged particle to accelerate? A) an electric field B) a constant magnetic field C) a neutron field D) charged particles do not accelerate E) a gravitational field
A) a electric field E) a gravitational field
Anthony Davis's ball travels in an arc. After it reaches its highest point and falls towards the basket, A) its velocity increases B) its velocity remains constant C) its acceleration increases D) the acceleration is constant E) the acceleration is zero
A) its velocity increases D) the acceleration is constant
A battery works because it A) pumps positive charge from its negative terminal to its positive terminal B)creates a positive charge C)creates a negative charge D)pumps positive charge from its positive terminal to its negative terminal E) it depends on the type of battery
A) pumps positive charge from its negative terminal to its positive terminal
You are cutting a limb off a bush with a folding saw. You have to push the saw away from you as it moves away from you and you pull the saw towards you as it moves towards you. When are you doing positive work on the saw? A) while pulling B) while pushing C) not while pulling D) not while pushing E) it depends on the size of the blades
A) while pulling
Why can't an audio amplifier operate without batteries or a power supply?
ALL OF ABOVE*** To produce a more powerful copy of an input signal, the amplifier needs a source of energy To produce a more powerful copy of an input signal, the amplifier needs a source of current To produce a more powerful copy of an input signal, the amplifier needs a source of voltage
When you kick a football for a game winning field goal, which pushes on the other harder: your foot or the football? A) it depends on the mass of the football B) Both push equally C) Your foot pushes harder D) The football pushes harder E) It depends on the weight of the ball
B) Both push equally
You are unhappy with the Physics professor Barish, and start an online campaign to fund a sabbatical for him to go to the moon to spare future students. Unbeknownst to the students the following quarter, Barish has made arrangements to deliver the course remotely so the "show can go on" and he loves teaching. Barish begins talking about mass, weight, and related things. He correctly makes which of the following statement: A) His weight is still essentially unchanged but his mass is less than on earth B) His mass is still essentially unchanged but his weight is less than on earth C) neither his weight of his mass have changed D) his weight and mass have significantly changed E) He is weightless
B) His mass is still essentially unchanged but his weight is less than on earth
A stroller with a baby is traveling down the sidewalk at a constant speed and not changing direction. It is experiencing wind resistance, gravity, and frictional forces from the pavement. What can be said about the stroller's acceleration? A) It is accelerating because there are forces acting on it B) It is not accelerating because it has a constant velocity C)It is not accelerating because gravity holds it down. D) It is accelerating because you are propelling the stroller forward E)It is not accelerating because the stroller has wheels
B) It is not accelerating because it has a constant velocity
Several bottles are lying on their sides on the table. They contain different amounts of liquid, but the bottles are not see-through. How can you find the full bottle without lifting anything? A) Blow on the bottles with equal forces and see which one accelerates the most B) Push on the bottles with equal force and see which one accelerates the least C) Compare the velocities of the cans D) Compare the positions of the bottles E) There is no way of telling without lifting
B) Push on the bottles with equal force and see which one accelerates the least
A personal negative ion generator sits near your nose and purifies the air around your mouth and nose by electrically charging the particles in the air. Why will those charged particles stick to neutral surfaces, such as your shirt? A) the premise is wrong. The charged particles will never stick to a neutral surface; only a surface that has an opposite charge. B) The charged particles polarize the neutral surfaces C) The charged particles will induce opposite charge in the neutral surfaces D) The charges particles will oppositely charge the neutral surfaces when they come in contact
B) The charged particles polarize the neutral surfaces
A coffee grinder has a blade that rotates and cuts the coffee beans into small pieces. Nothing prevents the coffee beans from moving. Why don't the beans get out of the way when the blade begins to push on them? A) Gravity holds them in place B) They have inertia C) The beans are stuck together D) The blade is sharp E) The blade is moving very rapidly
B) They have inertia
You have covered a grounded metal surface with metal surface with a layer of photo conductor. Working in the dark, you sprinkle negative charge onto this surface. If you now expose only the right half of the photo conductor to light, you will find that A) negative charge flows from the right side of the photo conductor to the left and both sides become neutral B) the right half becomes neutral while the left half remains negatively charged C) the left half becomes neutral while the left half remains negatively charged D) Nothing happens because there is no changing magnetic field E) Negative charge flows from the left side of the photo conductor to the right and both sides become neutral
B) the right half becomes neutral while the left half remains negatively charged
You remove the batteries from a working flashlight with an incandescent bulb, they turn both of them around as a pair, and reinsert them in the flashlight. They make good contact with the flashlight's terminals at both ends, so that there is no mechanical problem preventing the flashlight from working. If you now switch on the flashlight, it will A) not work because only electrons can actually move through a circut. The positively charged atomic nuclei are immobile B) work properly, although current will now be flowing backward through its circuit C) not work because the batteries can't send current backward through the flashlight's circuit D) not work because the light bulb can only carry electric current in one direction E) will work momentarily, but then the bulb will burn out
B) work properly, although current will now be flowing backward through its circuit
Which direction does the electric field point around the positive terminal of a lithium battery? A) the electric field points towards the positive terminal's surface B) the electrical field does not leave the inside of the alkaline battery C) electric fields are not real, just a mathematical construction D) the electric field points away from the positive terminal's surface E) the electric field is a scalar quantity and therefore has no direction
D) the electric field points away from the positive terminal's surface
You are pushing your baby sister up a steep hill in her stroller, exerting a large force on the stroller. Your sister is traveling in a straight line at a constant speed. The net force she experiences is A) both forward and backward B) in the forward direction C) in the backward direction D) zero E) changing
D) zero
A coconut falls from a tree located 9.8 m above the ground. After 1 s of falling, the coconut's velocity will be 9.8 m/s downward. Why hasn't the coconut hit the ground? A) Air resistance held it back B) The gravity is weaker farther from the Earth, so it wasn't going fast enough when it started falling. C) This is incorrect. The coconut has hit the ground after 1s of falling D) The coconut's average speed for the 1 s is less than 9.8 m/s E) You catch the coconut just before it hits the ground and goes splat, leaving the coconut intact
D) The coconut's average speed for the 1 s is less than 9.8 m/s
Your younger brother is learning to skateboard. You push him so that he is moving at a constant velocity, but let it go as he approaches a hill. He rolls up, momentarily comes to a stop, and then rolls it back down. What direction is he accelerating a) as he rolls uphill? b) as he rolls downhill? A) a) downhill; b) uphill B) a) uphill; b) downhill C) a) zero; b) downhill D) a) downhill; b) downhill E) a) uphill; b) uphill
D) a) downhill; b) downhill
You throw an apple directly upward, after which it falls back into your hand. At the highest point of it's path, A) it experiences no forces B) it stops accelerating C) its accelerations changes D) its vertical velocity is zero E) its horizontal velocity changes
D) its vertical velocity is zero
On rainy days you often see oil films on the surfaces of puddles. Why do these films appear brightly colored?
Light reflects from the top and bottom surfaces of an oil film and the two reflections interfere with one another and the type of interference, constructive or destructive, depends on the film's thickness as well as the light's wavelength.
The Empire State Building in Manhattan has several FM antennas on top, added in part to increase its overall height. These antennas aren't very tall. Why do short antennas, located high in the air, do such a good job of transmitting FM radio?
FM transmission involves high-frequency, short wavelength radio waves and since a good antenna is one-quarter wavelength long, FM radio transmission requires relatively short antennas
When your reciever is too far from AM KSPN, you can only hear the loud parts of the transmission. In contrast, when it's too far from FM KUCR, you lose the whole sound all at once. Which of the following statement(s) are correct?
In AM transmission, the radio wave is strongest during the loudest portions of the broadcast In FM transmission, the radio wave intensity is constant
KUCR, UCR's FM Radio station, instructs your radio receiver how to move its speaker cone by varying the
Frequency of the radio wave it produces.
The index of refraction of Diamond is 2.42. If you put a diamond in water, you see reflections from its surfaces. However, if you put it in a liquid with an index of refraction of 2.42, the diamond is invisible. Why is it invisible, and how is this effect useful to a jeweler or gemologist?
If the liquid and diamond have the same index of refraction, then light doesn't change speed on entry to or exit from the diamond and no light reflects from the interface between the two. WHY: Reflection occurs when the speed of light changes in materials. If the speed does not change, there will be no reflection. The reflection occurs because the electric part of the wave loses energy as it accelerates charges in the material, while the magnetic part of the wave is unaffected. However, an electromagnetic wave must have a balance between the electric and magnetic parts of the wave. As a consequence, the magnetic part loses a comparable amount of energy causing some of the light to reflect
Why doesn't increasing the current passing through an LED affect the color of its light?
Increasing the current will result in a brighter LED but the color of light produced by the LED is determined primarily by the anode's bandgap in the LED's semiconductor.
Use the concepts of refraction, reflection, and dispersion to explain why a diamond emits a spray of colored lights when sunlight passes through its cut facets.
Light refracts and disperses as it enters the diamond, reflects from the back surface, and refracts and disperses as it exits the diamond. WHY: Light bends and disperses on entry, reflects from the back surface, and bends and disperses more on exit from the diamond.
Dish-shaped reflectors are used to steer microwaves in order to establish communication links between nearby buildings. Those reflectors are often made from metal mesh. Why don't they have to be made from solid metal sheets?
Microwaves will not respond to holes in the metal that are significantly smaller than their wavelengths
When two medium-sized nuclei are stuck together during an experiment at a nuclear physics lab, the result is usually a large nucleus with too few neutrons to be stable. The nucleus soon falls apart. Why could more neutrons make it stable?
Neutrons would experience the attractive nuclear force while diluting the repulsion between protons
If you are wearing polarizing sunglasses and want to see who else is wearing polarizing sunglasses, you only have to turn your head sideways and look to see which people now have sunglasses that appear completely opaque. Why does this test work?
Polarizing sunglasses normally block horizontally polarized light, so when you look at someone's eyes when they are wearing polarizing sunglasses, you see only vertically polarized light. Tilting your head sideways will allow your sunglasses to block vertically polarized light and thus you will see no light coming from the eyes of other people wearing polarizing sunglasses.
The gate of a MOSFET is separated from the channel by a fantastically thin insulating layer. This layer is easily punctured by static electricity, yet the manufacturers continue to use thin layers. Why would thickening the insulating layer spoil the MOFSET's ability to respond to charge on its gate?
The gate's charge must be very near the channel in order to attract opposite charges and draw the charge into the channel.
If you hold your camera up to a small hole in a fence, you will be able to take a picture of the scene on the other side. However, the exposure time will have to be quite long, and the depth of focus will be surprisingly large. Explain.
The hole effectively reduces the diameter of the camera lens and small diameter lenses have large depths of focus because the few light rays that manage to get through the small opening are already close to one another but they require longer exposures because so little light passes through the narrow lens opening.
A CD player uses a beam of laser light to read the disc, focusing that light to a spotless that 1 µm (10-6 m) in diameter. Why can't the player use a cheap incandescent lightbulb for this task, rather than a more expensive laser?
The incandescent lightbulb's photons are all different and therefore will not focus on the same tiny spot.
If you hold a permanent magnet the wrong way in an extremely strong magnetic field, its magnetization will be permanently reversed. What happens to the magnetic domains inside of the permanent magnet during this process?
The magnetic domains of the permanent magnet that are aligned with the applied magnetic field grow while the domains opposite to the applied magnetic fields shrink
If you connect the output of one inverter to the input of a second inverter, how will the output of the second inverter be related to the input of the first inverter?
The output of the second inverter will be the same as the input to the first inverter.
AM Radio station KSPN 710 claims to transit 50,000 W of music power, but that's actually its average power. There are times when it transmits more power than that and sometimes when it transmits less. Explain.
The power being transmitted is changed in order to represent air pressure fluctuations with the radio wave: compressions are represented by strengthening the radio wave and refractions are represented by weakening the radio wave.
Why is it difficult or impossible to make very small atomic bombs?
The smaller the nuclear fuel component, the more likely it is that a neutron will escape before it causes a fission and the less efficient the fuel is at using fission neutrons to sustain a chain reaction.
When a sodium atom is in its lowest excited state, it can emit light. Why?
The sodium atom can undergo a radiative transition to its ground state, thereby emitting a photon of light.
In an n-channel MOSFET, the source and drain are connected by a thin strip of p-type semiconductor. Why is this device labeled as having an n-channel rather than a p-channel?
The strip of p-type semiconductor becomes effectively n-type when extra electrons are drawn into it by nearby positive charge on its gate.
