Questions and Answers
What do polarizing sunglasses normally block?
What happens when you tilt your head sideways while wearing polarizing sunglasses?
You will see no light coming from the eyes of other people wearing polarizing sunglasses.
Why does the type of illumination affect appearances in makeup mirrors?
Incandescent light has less blue and more red than fluorescent light.
What causes the sodium atom to emit light?
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Why is a discharge in a mixture of gases more likely to emit a full white spectrum of light?
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Why would a neon sign emit almost no visible light if filled with low-pressure mercury vapor?
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Why doesn't increasing the power to a neon sign change its color?
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What happens to a photoconductor's ability to conduct electricity when exposed to light?
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Why can't a CD player use a cheap incandescent lightbulb instead of a laser?
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Why is the highest energy valence level in a diode laser's p-type anode important?
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Why doesn't increasing current through an LED affect its light color?
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How many electrons can occupy the same orbital without violating the Pauli exclusion principle if they have four different internal states?
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What effect does thermal energy have on the ability of a semiconductor to conduct electricity?
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Why does laser light exhibit strong interference effects?
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What happens to light in a typical laser?
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Why do the sides of a glass vase filled with water appear shiny?
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What is the main reason a DVD can hold more information than a CD?
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What causes light to follow a glass fiber almost indefinitely?
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Why does gravity not stop a dolphin from leaving the water?
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Does a horizontal force keep you moving forward when you jump across a small stream?
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Why don't coffee beans move out of the way when a grinder's blade pushes on them?
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What can be said about a car traveling at constant speed and direction?
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As you hit your brakes to avoid a dog, in which direction is your acceleration directed?
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If you are backing up but slowing down, in which direction is your acceleration directed?
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What is the vertical velocity of a projectile at the top of its path?
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Why hasn't an acorn that falls from a height of 9.8 m reached the ground after 1 second?
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What would be a reasonable response to the joker's question about gravity?
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What happens to a person's mass and weight when on Mars?
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What is the net force experienced by a water-skier being pulled at constant speed?
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When you kick a soccer ball, who pushes harder: your foot or the soccer ball?
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When are you doing positive work on a handsaw?
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Match the direction of acceleration for a steel ball rolling on a tilted surface:
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What happens to a truck's kinetic energy when it rolls up a runaway truck ramp?
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Why don't two Ping-Pong balls normally exert electrostatic forces on each other?
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Why will charged smoke particles stick to walls and furniture?
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What happens when two pieces of adhesive tape are extracted from a dispenser?
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How does the electrostatic potential energy compare between positive charges on a battery's terminals?
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Why is it important to stand on an electrical insulator when using a Van de Graff generator?
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How does Coulomb's law explain the electric field around a charged hairbrush?
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Which way does the electric field point around the positive terminal of an alkaline battery?
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What happens when you sprinkle negative charge onto a grounded metal surface and expose part of it to light?
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What should you expect to happen near the static dissipaters of an airplane flying through neutral air after flying through a negatively charged cloud?
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Which of the following can cause a charged particle to accelerate?
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If you reverse the batteries in a flashlight that fits properly, what will happen?
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Why wouldn't a lamp light if only one prong of a power cord is plugged into an outlet?
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Why must the filament of a lightbulb have a much larger electrical resistance than the supporting wires?
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What happens when a lamp cord creates a short circuit?
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What does a battery do?
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Why do two button magnets have decreasing attractive forces as they separate?
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Why do a button magnet and an iron pipe attract each other?
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Which of the options regarding a bar magnet's poles is physically possible?
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What happens to the magnetic domains inside a permanent magnet held wrong in a strong magnetic field?
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What happens to the magnetic domains inside a permanent magnet that is hammered or heated?
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Do more magnetic flux lines begin or end on a button magnet, or are those numbers equal?
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What happens when a strong magnet is dropped through a copper pipe?
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Why does a north pole of a magnet fall slower onto an aluminum sheet?
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Why must an ID or credit card be swiped quickly past a coil of wire to read its magnetic strip?
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Why is the current in a coil of wire related to its motion in a microphone?
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Why is an electromagnetic wave expected to have both electric and magnetic fields?
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How do FM radio waves control a speaker cone's movement?
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Why does an AM radio station transmit varying power?
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What happens when your receiver is too far from an AM radio station?
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Why do short antennas do well for FM radio transmission?
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Why are porous ceramics unsuitable for use in a microwave oven?
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Why are most microwave TV dinners packaged in plastic rather than aluminum trays?
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Compare how a potato cooks in a microwave oven with how it cooks in an ordinary oven.
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Why don't dish-shaped reflectors for microwaves need to be made of solid metal sheets?
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What causes synchrotron radiation from a fast-moving charged particle in a magnetic field?
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Why can astronauts on the moon see stars even with the sun overhead?
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What explains why a diamond emits a spray of colored lights when sunlight passes through it?
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Why does a diamond become invisible in a liquid with the same index of refraction?
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Why do oil films on puddles appear brightly colored?
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Why do polarizing sunglasses help identify others with the same type of sunglasses?
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Study Notes
Inertia and Motion
- Dolphins can leap out of water due to inertia, not gravity.
- Jumping across a stream does not require a horizontal force as inertia maintains forward motion.
- Coffee beans remain in place when cut by rapidly rotating blades due to inertia.
Forces and Acceleration
- A car traveling at constant speed experiences no acceleration despite external forces.
- Braking while driving north results in acceleration directed south.
- When reversing but slowing down, acceleration is directed forwards.
Projectile Motion
- A projectile thrown straight up has a vertical velocity of zero at its peak.
- An acorn falling from 9.8 m will have a downward velocity of 9.8 m/s after one second but hasn't hit the ground due to lower average speed.
Gravity and Acceleration
- The acceleration due to gravity (9.8 m/s²) does not mean all objects accelerate; net external forces also play a role.
- An instructor's mass remains unchanged on Mars, but weight decreases due to lower gravitational pull.
Forces in Motion
- A water skier being pulled at constant speed by a speedboat experiences a net force of zero.
- Forces between your foot and a soccer ball are equal and opposite when kicking.
Work and Energy
- Positive work is done on a handsaw both when pushing and pulling it.
- Kinetic energy of a truck converts to gravitational potential energy when it rolls up a ramp.
Electric Forces
- Two charged Ping-Pong balls repel each other due to cancellation of electrostatic forces.
- Charged smoke particles from an ion generator adhere to neutral surfaces by polarizing them.
Charge Distribution and Behavior
- Adhesive tape repels when extracted because each acquires like charges.
- A positive charge on a battery’s terminal has higher electrostatic potential energy than on the negative terminal.
Static Electricity
- Insulation on which one stands is crucial for static charges to remain on the body.
- An electric field points away from the positive terminal of a battery.
Photoconductors and Light
- Exposing only part of a charged photoconductor to light neutralizes that area while the rest stays charged.
- Static dissipaters on airplanes cause corona discharge, releasing charges into the air.
Electromagnetic Forces
- Charged particles can accelerate under gravitational and electric fields.
- Rearranging batteries in a flashlight does not hinder its function; current will still flow.
Power and Resistance
- Filament resistance in lightbulbs is crucial for consuming electrical power efficiently.
- A short circuit bypasses the bulb, preventing it from lighting.
Magnetic Forces
- Separation distance significantly affects the magnetostatic forces between two magnets.
- A magnet polarizes nearby materials, causing attraction rather than repulsion.
Light and Wave Behavior
- Light's interaction with a diamond leads to refraction, reflection, and dispersion, creating colorful effects.
- Oil films create color patterns due to interference between reflected light.
Perception and Color
- Polarizing sunglasses block horizontally polarized light, which affects visibility when head position changes.
- The type of bulb affects appearance due to differences in light color composition.
Atomic Emission
- Sodium atoms emit light when undergoing transitions from excited states to ground states.
- A mixture of gases emits a broader spectrum of light due to varied radiative transitions.
Mercury Vapor and Light
- Low-pressure mercury vapor primarily emits ultraviolet light, making it nearly invisible to the human eye.### Incandescent Bulbs vs. Neon Signs
- Increasing power to an incandescent bulb raises filament temperature and light whiteness, emitting thermal radiation with a blackbody spectrum.
- Neon signs are not thermal light sources; increased power brightens them but does not alter color, as their spectrum remains unchanged.
Xerographic Copiers
- Xerographic copiers utilize a photoconductor surface that responds to light, controlling black powder placement on paper.
- In darkness, the photoconductor cannot conduct electricity because electrons fill its valence levels.
Photoconductor Properties
- Exposure to light enables photoconductors to switch from insulating to conducting by moving electrons from the valence band to the conduction band.
CD Players and Laser Use
- CD players employ laser light focused to a diameter under 1 µm to read discs, as incandescent bulbs produce varying photon wavelengths, preventing focus.
Diode Lasers Efficiency
- For diode lasers, if high-energy valence levels are occupied, absorption of laser light occurs, trapping radiation and decreasing light emission efficiency.
LED Color Emission
- The color of light from an LED remains constant regardless of increased current, as it primarily depends on the band gap of the semiconductor in the anode.
Pauli Exclusion Principle
- A maximum of four distinguishable electrons can occupy the same orbital without violating the Pauli exclusion principle.
Semiconductor Conductivity
- Elevated thermal energy enables electron shifts in hot semiconductors from valence to conduction levels, enhancing electrical conductivity.
Laser Light Characteristics
- Laser light exhibits strong interference effects due to its coherence and monochromatic nature, unlike other light sources such as flashlights.
Amplification in Lasers
- In typical lasers, the correct light color bounces between two mirrors and is amplified by excited atoms in the laser medium.
Photon Interference
- Photons from laser beams interfere due to their cohesive wave nature, while sunlight photons, being independent waves, can only interfere with themselves.
Photography and Lenses
- Sports photographers rely on large aperture, long focal length lenses, which produce a small depth of focus, affecting image sharpness.
- For blurry foreground/background in portraits, use the largest aperture with a short shutter speed to control exposure and focus.
Camera Exposure Mechanics
- A small hole reduces lens diameter, resulting in a large depth of focus, though longer exposure times are necessary as less light enters.
Zoom Lenses and Focal Length
- Zoom lenses in cameras, especially on telephoto settings, indicate longer focal lengths, bringing distant objects closer.
Lens Diameter Impact
- Increasing a camera lens diameter while maintaining focal length brightens the image and reduces depth of focus, compromising simultaneous clarity at various distances.
Blue vs. Infrared Laser Beams
- The width of a laser beam waist is influenced by light wavelength; blue lasers produce narrower beams due to shorter wavelengths compared to infrared lasers.
Glass and Total Internal Reflection
- The shiny appearance of a glass vase filled with water is due to total internal reflection of light within the glass sides.
DVD Data Density Compared to CD
- DVDs hold more information than CDs mainly because they use shorter-wavelength light for data reading, enhancing storage capacity.
Light Propagation in Fiber Optics
- Glass fibers allow light to travel indefinitely with minimal loss due to total internal reflection when light tries to escape at shallow angles.
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Description
Explore the concepts of polarizing sunglasses and how they manipulate light. Understand how horizontally and vertically polarized light interact with different surfaces, and the effect of tilting your head on visibility. This quiz delves into everyday applications of optics in fashion and technology.