Optics and Polarization

Questions and Answers

What do polarizing sunglasses normally block?

Vertically polarized light

Horizontally polarized light (correct)

Both vertically and horizontally polarized light

None of the above

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?

It undergoes a radiative transition to its ground state, emitting a photon of light. Signup and view all the answers

Why is a discharge in a mixture of gases more likely to emit a full white spectrum of light?

The presence of different atoms and molecules allows for more variety in radiative transitions. Signup and view all the answers

Why would a neon sign emit almost no visible light if filled with low-pressure mercury vapor?

Excited mercury atoms emit primarily invisible ultraviolet light. Signup and view all the answers

Why doesn't increasing the power to a neon sign change its color?

The sign is not a thermal light source, so increasing power only brightens the light. Signup and view all the answers

What happens to a photoconductor's ability to conduct electricity when exposed to light?

It goes from insulating to conducting. Signup and view all the answers

Why can't a CD player use a cheap incandescent lightbulb instead of a laser?

Incandescent lightbulb's photons are all different and will not focus to the same tiny spot. Signup and view all the answers

Why is the highest energy valence level in a diode laser's p-type anode important?

If these levels aren't empty, it can absorb laser light and reduce the diode's ability to emit light. Signup and view all the answers

Why doesn't increasing current through an LED affect its light color?

The color of light produced is determined by the anode's band gap. Signup and view all the answers

How many electrons can occupy the same orbital without violating the Pauli exclusion principle if they have four different internal states?

Any number from 0 to 4 electrons. Signup and view all the answers

What effect does thermal energy have on the ability of a semiconductor to conduct electricity?

Increases the ability to conduct electricity. Signup and view all the answers

Why does laser light exhibit strong interference effects?

Because laser light is both coherent and monochromatic. Signup and view all the answers

What happens to light in a typical laser?

It is amplified by the excited atoms in the laser medium. Signup and view all the answers

Why do the sides of a glass vase filled with water appear shiny?

Because of total internal reflection. Signup and view all the answers

What is the main reason a DVD can hold more information than a CD?

DVDs use shorter-wavelength light than CDs. Signup and view all the answers

What causes light to follow a glass fiber almost indefinitely?

Perfectly reflected whenever it tries to leave the glass at a shallow angle. Signup and view all the answers

Why does gravity not stop a dolphin from leaving the water?

The dolphin has inertia as it approaches the surface. Signup and view all the answers

Does a horizontal force keep you moving forward when you jump across a small stream?

No, there is no horizontal force. Signup and view all the answers

Why don't coffee beans move out of the way when a grinder's blade pushes on them?

They have inertia. Signup and view all the answers

What can be said about a car traveling at constant speed and direction?

It is not accelerating because it has constant velocity. Signup and view all the answers

As you hit your brakes to avoid a dog, in which direction is your acceleration directed?

South. Signup and view all the answers

If you are backing up but slowing down, in which direction is your acceleration directed?

Forwards. Signup and view all the answers

What is the vertical velocity of a projectile at the top of its path?

Zero. Signup and view all the answers

Why hasn't an acorn that falls from a height of 9.8 m reached the ground after 1 second?

The acorn's average speed for the 1s is less than 9.8 m/s. Signup and view all the answers

What would be a reasonable response to the joker's question about gravity?

Gravity is just part of the story and it is the total net external force that determines acceleration. Signup and view all the answers

What happens to a person's mass and weight when on Mars?

His mass is still essentially unchanged but his weight is less than on Earth. Signup and view all the answers

What is the net force experienced by a water-skier being pulled at constant speed?

Zero. Signup and view all the answers

When you kick a soccer ball, who pushes harder: your foot or the soccer ball?

Both push equally. Signup and view all the answers

When are you doing positive work on a handsaw?

Both while pushing and pulling. Signup and view all the answers

Match the direction of acceleration for a steel ball rolling on a tilted surface:

As it rolls uphill = Downhill As it rolls downhill = Downhill Signup and view all the answers

What happens to a truck's kinetic energy when it rolls up a runaway truck ramp?

It converts into gravitational potential energy. Signup and view all the answers

Why don't two Ping-Pong balls normally exert electrostatic forces on each other?

The electrostatic forces cancel due to zero net charges on each ball. Signup and view all the answers

Why will charged smoke particles stick to walls and furniture?

The charged smoke particles polarize the neutral surfaces. Signup and view all the answers

What happens when two pieces of adhesive tape are extracted from a dispenser?

Each piece of tape will acquire like charges while being extracted from the tape dispenser. Signup and view all the answers

How does the electrostatic potential energy compare between positive charges on a battery's terminals?

A positive charge on the battery's positive terminal will have more electrostatic potential energy than on its negative terminal. Signup and view all the answers

Why is it important to stand on an electrical insulator when using a Van de Graff generator?

Standing on an insulator allows you to retain the charges transferred from the static generator. Signup and view all the answers

How does Coulomb's law explain the electric field around a charged hairbrush?

The electrostatic forces between the hairbrush and a positive charge diminish with increasing separation distance which results in a smaller electric field. Signup and view all the answers

Which way does the electric field point around the positive terminal of an alkaline battery?

The electric field points away from the positive terminal's surface. Signup and view all the answers

What happens when you sprinkle negative charge onto a grounded metal surface and expose part of it to light?

The left half becomes neutral while the right half remains negatively charged. Signup and view all the answers

What should you expect to happen near the static dissipaters of an airplane flying through neutral air after flying through a negatively charged cloud?

A corona discharge at the dissipater tips will spray negative charge into the air. Signup and view all the answers

Which of the following can cause a charged particle to accelerate?

Both A and B Signup and view all the answers

If you reverse the batteries in a flashlight that fits properly, what will happen?

It will work properly, although current will now be flowing backward through its circuit. Signup and view all the answers

Why wouldn't a lamp light if only one prong of a power cord is plugged into an outlet?

No current flows because by using only one prong, an open circuit is created and thus the lamp cannot glow. Signup and view all the answers

Why must the filament of a lightbulb have a much larger electrical resistance than the supporting wires?

A larger electrical resistance has a larger voltage drop and thus consumes more electrical power. Signup and view all the answers

What happens when a lamp cord creates a short circuit?

Current will bypass the bulb and the bulb will not light up. Signup and view all the answers

What does a battery do?

It pumps positive charge from its negative terminal to its positive terminal. Signup and view all the answers

Why do two button magnets have decreasing attractive forces as they separate?

As separation distance increases, the distance separating the two pairs of poles is very small and therefore the attractive and repulsive forces nearly cancel. Signup and view all the answers

Why do a button magnet and an iron pipe attract each other?

The button magnet's magnetic field polarizes the iron pipe and the pipe develops an opposite pole near the approaching pole of the button magnet and thus attracts the magnet. Signup and view all the answers

Which of the options regarding a bar magnet's poles is physically possible?

Remove its magnetic poles altogether Signup and view all the answers

What happens to the magnetic domains inside a permanent magnet held wrong in a strong magnetic field?

The magnetic domains of the permanent magnet that are aligned with the applied magnetic field grow while the domains opposite to the applied magnetic field shrink. Signup and view all the answers

What happens to the magnetic domains inside a permanent magnet that is hammered or heated?

The magnetic domains will lose their uniform orientations and become more randomly oriented. Signup and view all the answers

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. Signup and view all the answers

What happens when a strong magnet is dropped through a copper pipe?

The magnet descends slowly because its motion causes currents to flow in the pipe and those currents repel the magnet. Signup and view all the answers

Why does a north pole of a magnet fall slower onto an aluminum sheet?

Current induced in the aluminum by the approaching north pole produces a repelling north pole on the aluminum's surface. Signup and view all the answers

Why must an ID or credit card be swiped quickly past a coil of wire to read its magnetic strip?

A moving magnet will induce a current in the coil so that the magnetic strip can be read. Signup and view all the answers

Why is the current in a coil of wire related to its motion in a microphone?

As the 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. Signup and view all the answers

Why is an electromagnetic wave expected to have both electric and magnetic fields?

An electromagnetic wave must have a magnetic field that changes with time to produce its electric field. Signup and view all the answers

How do FM radio waves control a speaker cone's movement?

By varying the frequency of the radio wave it produces. Signup and view all the answers

Why does an AM radio station transmit varying power?

The power being transmitted is changed in order to represent air pressure fluctuations with the radio wave. Signup and view all the answers

What happens when your receiver is too far from an AM radio station?

You can only hear the loud parts of the transmission. Signup and view all the answers

Why do short antennas do well for FM radio transmission?

FM radio transmission involves high-frequency, short-wavelength radio waves, which require relatively short antennas. Signup and view all the answers

Why are porous ceramics unsuitable for use in a microwave oven?

Water molecules trapped in the ceramics would convert the energy of the microwaves into thermal energy and the ceramic would become extremely hot. Signup and view all the answers

Why are most microwave TV dinners packaged in plastic rather than aluminum trays?

Aluminum trays would reflect the microwaves which would result in improperly cooked food. Signup and view all the answers

Compare how a potato cooks in a microwave oven with how it cooks in an ordinary oven.

In a microwave oven, the potato's water absorbs microwaves, rising uniformly in temperature, while in an ordinary oven, heat flows gradually inwards, leading to uneven cooking. Signup and view all the answers

Why don't dish-shaped reflectors for microwaves need to be made of solid metal sheets?

Microwaves will not respond to holes in the metal that are significantly smaller than their wavelengths. Signup and view all the answers

What causes synchrotron radiation from a fast-moving charged particle in a magnetic field?

Without the magnetic field, the charged particle would travel at a constant velocity and would not radiate electromagnetic waves because of its constant velocity. Signup and view all the answers

Why can astronauts on the moon see stars even with the sun overhead?

The scattered light from the sun is so bright that it overwhelms the dim light from the stars. Signup and view all the answers

What explains why a diamond emits a spray of colored lights when sunlight passes through it?

Light refracts and disperses as it enters the diamond, reflects from the back surface, and refracts and disperses as it exits the diamond. Signup and view all the answers

Why does a diamond become invisible in a liquid with the same index of refraction?

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. Signup and view all the answers

Why do oil films on puddles appear brightly colored?

Light reflects from the top and bottom surfaces of an oil film, causing interference that depends on the film's thickness and the light's wavelength. Signup and view all the answers

Why do polarizing sunglasses help identify others with the same type of sunglasses?

Turning your head sideways allows you to see which people have sunglasses that appear completely opaque. Signup and view all the answers

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.