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Exam 3- ppt

Terms in this set (76)

Define electromagnetic wave (EM) and explain how they are created.
EM waves have electric fields, their motion creates magnetic fields, regenerating each other by electromagnetic conduction, allowing them to travek in a vaccum. They are created by vibrating electric charges
List two differences between sound and EM waves.
Sound waves are compressional waves and can only travel through a medium. EM waves are transverse waves that can travel through a vaccum. EM waves travel faster than sound waves.
List the seven types of EM waves. Indicate what EM wave are the most
energetic and the least energetic.
(from least to greatest) radio waves, microwaves, infared, visible light, ultraviolet, x rays and gamma ray-- higher frequency = higher energy
Define visible light. List what colors have the most and least frequency
Light we can percieve with our eyes, (greatest to least) violet, indigo, blue, green, yellow, orange, red.
Explain how Isaac Newton and Christian Huygens were trying to explain
the nature of light. Who won the argument?
Newton proposes that light is made out of particles of energy, Huygens thought light was made out of waves. Newtons theory could not explain interference, diffraction and polarization while Huygens theory could. Einstein discovers the photoelectric effect that shows light is a particle. Conclusion, light is both. It can be modeled as a particle or a wave.
Differentiate between transparent, translucent and opaque materials.
Transparent allows light to pass through the material so you can see whats on the other side. While opaque materials do not allow any light o pass through them so you can not see through them at all. While transluscent is a mixture, it allows light to travel through but it is scattered so you can partially see through those materials.
Explain why cars with their windows up become very hot, even though
the day may be relatively warm.
visible light goes through the car windows while infared and ultraviolet are blocked out. Visible light warms up the interior and seats and that warm temperature produces infared waves that can not escape bc they are unable to pass through the glass. --- infared waves are accumulated in the car and the heat energy can not escape.
Explain why a wet object looks darker than when dry.
On dry surfaces light is reflected directly to your eyes. While on a wet surface, light bounces inside the transparent wet region, absorbing energy, so there is less light reflected back to your eyes.
Define reflection. Explain the difference between specular and diffuse
reflection
is the returning of a wave to the medium through which it came when encountering a reflective surface. It bounces off and returns to a medium. Regular, specular is when a surface is really smooth. Irregular diffuse is when the surface is relatively rough
Use specular and diffuse reflection to explain why roads look dark at
night when wet.
The road acts a little bit like a mirror. the water covers the imperfections and roughness in teh road to make it smooth so most of the light is reflects forward, specular diffusion. While the dry roads create diffusion reflection bc the road is rougher.
State the law of reflection.
on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray.
For mirrors that are flat, concave (when close), concave (when far away),
and convex, describe (a) whether the image is virtual or real, (b) image
magnification, if any, and (c) whether the image is upright or inverted.
Flat-
a) virtual
b) no magnification
c)upright
Concave- far away close up
a)real virtual
b)reduced magnification increased
c)inverted upright
Convex-
a)virtual
b)reduced magnification
c)upright
Explain how flashlights and satellite dishes change the direction of EM
waves.
Using a concave reflector they both use the incoming light that is parallel and can be reflected so it's concentrated in a particular point
Define refraction. Explain the role of electrons in slowing down the speed
of light inside a transparent material.
The change in the direction of light when it goes from one medium to another. In transparent material, vibrating electrons emit protons of the same energy. The absorbing and reemiting takes time and the time delay slows the light down.
Describe the speed of light and the angle of refraction inside a material
with a (a) low index of refraction, like water or ice, and (b) high index of
refraction, like glass or diamond.
A) angle of light inside water is bigger and will move faster than glass or a diamond. B) the angle of light is smaller than water and will move slower than water. Diamond specifacally has highest optical density so it will slow down light the most and have the smallest angle
Use refraction ideas to explain why (a) fish appear closer to the surface
that they really are, (b) stars appear to twinkle, (c) the Sun appears closer to the horizon that it really is, and (d) why hot roads appear to be flooded.
a) brain percieves that the light is traveling in a straight line but it refracted so you see the fish in the apparent depth rather than the real depth. so you see the fish closer to the surface than they really are.
b)light travels through a vaccum but then travels through different layers within the atmosphere and air has a little bit of an index of refraction so it will change the direction of the light
c)air has an index of refraction so there is a change in the direction of the sunlight, so during sunset there is a ssudden drop
d)air changes direction of light due to temperature, closer to the road the air is warmer and higher it is cooler. The temperature makes it change direction
Define internal reflection. Use internal reflection to explain (a) the headless-lady and the "falling" green laser light in the PPT slides and (b) why diamonds look very shiny.
when the light tries to go from a more dense material to a less dense material and it cant get out.
a) stays within the material until it gets out for a laser. all the light we see stays within the water so we do not see he light above it.
c) slows down light, jewlers have cut in a particular way to where it comes in refracts to where it only escapes from the top and with a colorly pattern.
Explain the difference between converging and diverging lenses in terms of (a) location of thick and thin areas, and (b) how printed text looks like using each type of lens.
a)thicker in the middle and thin on the edges (convex)
thin in the middle and thicker on the edges(concave)
b) magnified(Convex)
smaller, reduced in size (concave)
Explain the difference between selective reflection and selective transmission. What do they have in common?
Selective reflection happens in opaque materials while transmission happens in trasparent materials. They both depend on the color of light so in selective reflection when the light is not a white light (red for example) all other colors will be absorbed similar to selective transmission it depends on the color of light and all others will be absorbed.
Describe what happens when a material has a certain color but the available light is of a different color.
it will turn black, the color will be absorbed
List the three primary light colors and what colors must be combined to produce (a) magenta, (b) yellow, (c) cyan, and (d) white.
A) red and blue
B) green and red
C)blue and green
D) red green and blue
Define dispersion. Explain how dispersion produces rainbows.
is the process of separation of light into colors arranged by frequency -- at just the right angle water droplets will refract light to create dispersion, seperation of colors to create a rainbow.
Define polarization. Describe what happens to light when (a) one vertically-aligned polarizer is placed in front of another vertically-aligned polarizer, and (b) one vertically-aligned polarizer is placed in front of horizontally-aligned polarizer.
is the alignment of transverse electric vectors in electromagnetic waves
a) passes through
b) light can not pass through the second polarizer
Define cornea, iris, pupil, lens, ciliary muscles, retina and optic nerve. Explain how the human eye works.
Cornea, outermost section, starts the refraction process then it goes through the pupil. the pupil is controlled by the iris that opens and closes the pupil and regulates how much light goes in. Then the lens inside your eye is flexible adn controlled by the ciliary muscles that push or pull the lense that allows one to focus vison to close or far away vision. Then the light reaches the back of the eye, the retina, there are photo and light receptors that covert light information into electrical singnal that goes out the optic nerve and to the brain. The brain identifies what you are seeing .
Explain the difference between cones and rods on the retina.
cones are responsible for color vision while rods are more sensitive and are responsible for light and dark vision.
Explain whether all animals (including humans) have similar color
vision.
humans have three cones while some animals such as a chickens have more than three cones. While dogs have two main cones. They do not see colors the same, the more cones, the more colors they are suseptiable to see.
Define nearsightedness. State what type of lens can be used to correct it
and why
where you can see nearby but things far away look kinda blurry. A concave or diverging lens can fix this because they make the light rays open up and focus at the retina.
Define farsightedness. State what type of lens can be used to correct it
and why.
you can see far away but near by objects look blurry. Reaches retina too early that not focused so a convex lens concentrates it at the retina.
Define astigmatism, glaucoma, daltonism (colorblindness), cataracts and
presbyopia.
astigmatism- your cornina is not perfectly round more of a oval
glaucoma-there is a increased pressure of fluid inside the eye, leading to damage to the optic nerve
daltonism- colorblindness, one or more cones are impaired
cataracts-lens gets cloudy/fuzzy which affects vision-- result of aging, trauma or heredity
presbyopia-occurs when the lens becomes less flexible, causing your near point to move father away. alittle like farsightenness and occurs with age.
Describe Aristotle's idea of (a) natural and (b) violent motion.
a)motion that occurs by itself, straight up or straight down
b)imposed motion resulting from an external push or pull
List three myths that Aristotle held about motion, and Galileo's correct explanations
-heavy objects fall faster than lighter ones; object will fall at the same time, mass is not a factor when there is not air resistance.
-a moving object must have a force exerted on it; in the absence of a force objects set in motion tend to continue moving indefineitly. object at rest will stay at rest and objects moving will remain at a constant speed
-velocity was a proportional force;the speed of motion is proportional to the force of the push.
Define inertia, and explain how mass and inertia are related.
Inertia is the tendency of a body to resist a change in motion or rest: mass is a measure of inertia, when a object has more mass it has more (resistance to change the state of motion)inertia
Use inertia ideas to explain (a) why coins remain stacked if you pull the paper strip quickly, (b) what string will break if you pull down quickly or slowly, and (c) how seatbelts work.
a) the coins have mass and inertia so they resist speeding up as you pull the paper. Only works because coins have a larger mass, plastic chips wouldnt work.
b) if you pull slowly the string on top will break first because it has more mass and pressure. If you pull fastly the bottom string will break because the ball has inertia so the bottom will breka.
c)if you are traveling at 50 mph in a car, you and everything in the car is also traveling at that speed. So if you hit a wall the car will slow down but you will not. You will continue your state of motion at 50 mph, seatbelts prevent you from continuing at that speed
Differentiate between (a) mass and weight and (b) mass and volume.
a)mass is the amount of matter in a object and is measured in kg and weight is the amount of gravitional pull on a object and is measured in newtons
b) mass is the amount of material while volume refers to the amount of space a object will occupy.
Differentiate between a force and a net force.
force is a push or pull, you can have more than one forces and all the forces in total is the net force.
State the equilibrium rule
if an object is not moving or at a constant speed that the forces acting on the object must balence or cancel out
Differentiate between static and dynamic equilibrium.
static- applies to when an object is not moving
dynamic- applies to when a object is moving at a constant speed
Define support force.
is a force that supports an object on the surface against gravity, net force is zero and it is in static equillibrium- also called normal force bc it acts perpendicular to the contact surface.
Define friction, and what three variables affect the friction between two surfaces.
is a type of force that slows one down or prevents them from moving.
- type and texture of materials
-how much they are pressed together
-Atomic "stickiness" on the surfaces.
Compare the applied force and the force of friction acting on a heavy object when an object is pushed and (a) it does not move, (b) it moves at a constant speed, and (c) it speeds up.
a) applied force and friction is the same
b) force of friction will match applied force
c)her force is stronger than the force of friction
Differentiate between a scalar and a vector.
scalar is a quanitity that only has a magnitude -a number and a unit-
vector- quanity that has a magnitude and direction- a number, unit and direction-
Differentiate between (a) distance and displacement, and (b) speed and velocity.
a)distance is the actual path a object takes from start ot finihs but displacement is the straight line between those.
b)speed is the time rate at which an object is moving along a path, while velocity is the rate and direction of an object's movement.
Explain why motion is said to be relative
need to know the frame of reference because everything is moving
Define acceleration, and list the three ways in which acceleration can occur
change in speed in a certain amount of time
-object changes direction
-object slows down
-object speeds up
define free fall
when acceleration is being produced by gravity
State by how much is the speed of an object decreasing each second, from the moment it is thrown upward to the moment it reaches its highest point
slows down by 10 meters per second
State by how much is the speed of an object increasing each second, from the moment it reaches its highest point to right before it hits the ground.
speeds up by 10 meters per second
Describe the shape of the trajectory of an object thrown at an angle.
will follow a parabolic path
Describe the horizontal and vertical motion of a projectile in terms of (a) speed (constant or changing) and (b) acceleration (constant or changing).
horizontal a) constant speed, no acceleration
vertical b) contant acceleration, changing speed
define force
a push or a pull that is capable of producing a change in motion
Describe whether an internal force can change the state of motion of an object.
they can not cause a change in motion, an object in motion will not change its motion unless its acted on by an external force.
Define inertia. Indicate the relationship between inertia and mass.
an objects resist to change in its state of motion.
the more mass an object has, the more inertia is has because it then has a greater tendency to resist changes in its state of motion
Use inertia ideas to explain (a) why the coin falls into the cup instead of being pushed forward, (b) how the tablecloth trick works, (c) why one string or the other will break depending on how quickly a force is applied, (d) How to get a hammer back in the handle.
a) the coin has inertia, will not speed up as the paper is removed.
b) objects have inertia so they resist the change in motion
c)bc there is more tension and the object resists the change in motion
Use inertia ideas to explain (a) why the coin in mid-air does not stay behind as the airplane moves forward and (b) why the bird in mid-air does not stay behind as the worm moves forward due to Earth's rotation.
a) they keep there inertia, the coin already had orginally speed as the person so it stays in place as it is flicked
b)both the earth adn teh warm have the same state of motion- realitve speed is zero
State Newton's second law of motion.
the force of mass is equal to its mass x acceleration
Describe the relationship between force and acceleration.
they are directly proportional, twice the force equals twice the acceleration
Describe the relationship between mass and acceleration.
mass and acceleration are inversely proportional because more mass, less accelertaion-- less mass, more acceleration
Use Newton's second law and the "π" analogy to explain why objects fall with the same acceleration even though heavy objects experience a stronger downward pull due to gravity (assume no air drag).
smaller circler, less circumfirance and less diamater-- while a larger circle has more circumfirace and more diameter so it cancels out and always equals 3.14

like f/m=g more force, more mass -- less force, less mass and cancels out to equal 10 meter per second
Use Newton's first and second laws to explain why a person speeds up as s/he falls, but can eventually reach a constant speed.
object will speed up until it reaches constant speed bc the weight and air resistance forces will balence out, this si known as terminal velocity
State Newton's third law of motion.
whenever an object exerts a force on a second object, the second object exerts an equal and opposite force on the first object
Use Newton's law to explain (a) why a cannon moves backward (recoils) at a slow speed and the cannonball moves forward at a high speed, and (b) why a rifle moves backward (recoils) at a slow speed and the bullet moves forward at a high speed.
a)the cannon ball has less mass so it has less inertia so it speeds up quickly whie the cannon has way more mass so there is recoil but much less acceleration. equal force
b)bullets have less mass-- they both have an equal force
State the correct explanation for each of the following 8 common force misconceptions shown in the lecture.
-only active agents exert a force-- you can have passive forces and still have a force. sitting in a chair
-motion implies active force- constant speed motion, they will just keep moving at constant speed
-no motion implies no force- an object that is not moving, has balenced forces
-veloctiy is proportional to the applied force- if you apply an external unbalanced force the object will continue to speed up as you continue to apply that force
-acceleration implies increasing force-an object will accelerate when you apply a net force
-force causes acceleration to a terminal speed-never will reach terminal speed if forces are unbalanced
-active force wears out- may transfer energy but force wont wear out
-mass makes things stop- friction will slow you down, wont stop bc its heavy but bc of an unbalence of an external force, friction or air resistance.
Explain the difference between rotation and revolution. Give one example of each type of circular motion.
axis of rotation is located inside the object that is roatation-earth
revolution- object goes around somethiing elese, axis of rotation is not apart of the object. - boy on a toyset that turns
Describe what happens to an object when a force is applied (a) in the direction of motion, (b) in the direction opposite to motion, and (c) perpendicular to the direction of motion.
a) speed up
b)slow down
c) change direction but not speed
Define centripetal force and describe three variables that are associated with it.
any force that causes an object to move in a circle.
-large mass, you want to move it faster and if you want a quicker change in direction
Describe what happens to the motion of an object if it was being swung in a circular motion and the string suddenly breaks.
object will travel in a straight line
Use the "object in the dashboard" example to explain whether centrifugal forces exist or not.
there is no such thing as a centrifugal force that pushes the objects outward when experiencing a circular motion. It is a perception caused by the car changing direction underneath the object. the car may be turning but the object will consistently move in a straight line
Contrast Aristotle and Newton's views on whether forces were universal or not depending on whether you were analyzing celestial or Earth events.
aristotle believed that stars, planets and the moon moved in divine circles free from the forces of earth and newton believed the force between the earth is the same force between the moon and the planets and everything else.
Describe the origin of the force keeping planets going around the Sun according to (a) Johannes Kepler, (b) Rene Descartes, and (c) Isaac Newton. Who had the correct explanation?
a)was magnetic in nature
b)planets motion was caused by vortices in the invisible planets and the sun were immerresed in.
c) the orgin of centripetal force must be gravitational: every mass pulls on every other mass.
State Newton's law of gravity.
every body in the universe attracts every other body with a mutually attractting force.
Explain the difference between "G" and "g".
G is the gravitational constant and g is accelertation due to gravity, 10 meters per second
Explain how Henry Cavendish measured the value of "G".
measured the force between attracting lead spheres with a torsion balance
Explain how Phillip von Jolly measured the value of "G".
method of measuring the attraction between two masses.
Explain the concept of weightlessness and how it is related to free fall.
objects that are free falling experience weightlessness because there is no support force; the body responds as if gravity forces were absent
Use Newton's law of gravity to explain where the value of "g" comes from.
g can be found out by earths mass divided by the earths radius
Describe how Newton's law of gravity explains (a) the discovery of Neptune, (b) the orbits of comets, (c) the oblateness of planets, and (d) the origin of tides.
a)postition of the planet and the predicted position based on math was not the same
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