Physics P2 Flashcards
Different types of reflection
Specular (smooth surface)and diffuse(rough surface)
What is rule for reflection
Angle of incidence is same as angle of reflection
Description of S-waves and P-waves
S-wave is transverse(secondary doesn’t go through liquid )
P-waves is longitudinal (Primary does go through liquid longitudinal like ripples in liquids) and is quicker than s-waves
What is the difference between a wave front diagram and a ray diagram
Wave front shows why the light refracts and changes direction by showing parts of the light slowing down
Ray diagram just shows the light reflecting and refracting
What is the symbol for concave and convex lenses in a ray diagram
Convex line with two arrows at the end pointing away
Concave line with two arrows at the end pointing in
What is the principle focus, focal length, lens axis in a concave and convex lens
Principle focus is where all the lines converge to in a convex lens and where the lines seem to come from in a concave lens
Focal length is the distance between the centre of the lens and the principle focus
Lens axis is the line going through the middle of the lens where if a light ray goes through it wont detract or change direction as the angle of incidence is 0
https://imgur.com/a/i1Yl9VB
What does diminished mean in terms of lenses
Means image has gotten smaller
Opposite of magnified
How do you draw a ray diagram
Draw a light ray from the top of image through the middle of the lens and axis
Draw another line from the top of the image parallel to the axis when it reaches the lens if convex it refracts towards the focal point if concave it follows the path of the focal point before the lens outward
The place the two lines meet is where the top of the real image is
If they don’t meet and are diverging then draw a dotted line going back and where the dotted lines meet is the top of the virtual image(where the image seems like it is coming from)
https://imgur.com/a/SjhOWDA
Example of Non contact force
Magnetic force, electrostatic force, gravity
Limit of proportionality
extension stops being proportional to force because it is inelastically deforming
Units for density of liquid
kg/m^3
What causes upthrust
When object is submerged in fluid a there is a force on it from every direction ,pressure increases with depth so force on bottom of the object is greater than force on top of an object that is submerged. The resultant force of this is upthrust
What is upthrust equal to
Upthrust is equal to the weight of the fluid that’s been displaced
Why will an object float or sink
If weight of object is more than upthrust it will sink, so if the weight of the object is more than the weight of the water displaced it will sink, so if density of object is more than density of water it will sink
Why is there less air pressure higher you go
Less air particles above so less of their weight decreasing pressure
And air gets less dense higher you go up because of gravity. Density decreasing means less particles to collide and cause pressure
What is Newtons first law
Object at rest stays at rest and object moving stays moving at constant speed unless force acted
Newtons second law
F =ma
Means objects with higher mass need more force to accelerate
And means the acceleration is directly proportional to amount of force
Newtons third law
Every action has opposite and equal reaction
What is stopping distance and what effects it
Thinking distance
Distance car travels during drivers reaction time
Factors affecting it are
Factors effecting it are
Drugs
Alcohol
Speed
Distractions
Tiredness
Braking distance
Distance car travels while the brakes are applied
Factors effecting it
Speed
Road conditions
Tire conditions
Brake quality
Units for momentum
(Kg m/s) m/s comes from velocity (p)in equations
Safety features in cars and how they help
Crumple zones ,seatbelts, air bags they increase the amount of time to stop so the change in momentum during a crash is over a long time decreasing the force on the body at a given time decreasing the chance of injury
How do you show the strength of magnetic field in a drawing
The more lines the stronger it is
How to draw magnetic field drawing
lines looping around going from north to south and lines from north going outwards and lines from south going inwards
How to know direction of magnetic field in wire
Use right hand thumb direction of current and fingers direction of magnetic field
What is a solenoid
A coil of wire each individual magnetic field of the wires add up creating a stronger magnetic field
What is motor effect
When wire carrying current is put through a magnetic field at 90 degrees it feels a force on it because of the interacting magnetic fields. If in parallel no force is exerted
What effects the force on a conductor in a magnetic field
The current going through the wire
Magnetic flux density
Length of wire
Can be seen in equation F = B I l
How to know direction of force in motor effect
Flemings left hand rule
thuMb Motion
First finger Field
SeCond finger Current
How do motors work
Coil of wire in a spindle in a magnetic field
Because the coil wraps around the current goes in two different directions meaning force is applied in two different directions causing it to spin the split ring make the contacts swap half way making motor rotate in the same direction
How does a speaker work
Coil of wire attached to a paper cone, coil goes around a pole and is surrounded by the other pole . When a AC current is passed through the coil of wire it goes back and forth every time the direction of current switches moving the cone and displacing the air making sound. The frequency of the AC is the same as the frequency of sound the speaker makes
What is the generator effect
When a conductor passes through a magnetic field and cuts them at 90 degrees a potential difference is induced and if the circuit is complete a current flows. If you move it back and forth the direction of the current changes making ac
Difference between slip ring and slip ring commutator
Slip ring is 2 different rings with brushes the brush stays in contact with the split ring at all times. Used in alternator generators where it produces ac
Slip ring is used in motors and dynamo generators. They are 2 half rings and the brushes change their connections with the slip rings every half turns. Used in motor to change direction of current in coil so it continues going the same direction. Used dynamos to create dc current
What is the difference between alternator and dynamos
Alternator creates ac current because it doesn’t have split rings commutator.
Dynamo created dc because of its split rings commutator . The connections swap every half turn
How does a microphone work
Diaphragm with coil attached different pressure waves move the diaphragm making the coil cut a magnetic field inducing an ac current through the coil.
What is transformer used for and what does more turns mean
Increase or decrease voltage in AC current .
The voltage is the same as the amount of turns, so if there is more turns in the secondary coil the voltage will be more if there is less turns in the secondary coil the voltage will be less
Describe life cycle of a star
Starts off as a cloud of dust and gas called a NEBULAR
Gravity pulls everything in and condenses it creating a protostar. In the PROTOSTAR the temperature rises and it gets more dense causing nuclear fusion to happen to hydrogen nuclei turning them into helium.
Star is now in its MAIN SEQUENCE a long stable period where the force of gravity and the force of fusion are equal.
Hydrogen begins to run out, for stars same size or smaller as the sun the star collapses inward making the temperature increase fusing helium nuclei into heavier elements up to iron then it swells up into a RED GIANT.
The red giant becomes unstable and ejects its outer layer of dust and gas leaving a hot dense core called WHITE DWARF fusion isn’t happening anymore so it starts to cool down into a BLACK DWARF
If the the star is bigger than our sun when it runs out of hydrogen it turns into a RED SUPER GIANT and heavier elements are made up to iron.
When fusion stops in the red super giant it explodes into a SUPER NOVA creating heavier than iron element and eject them out into space.
The outside layer of gases in a super nova are blown away leaving the centre of the super nova which turns into a neutron star if the star is big enough it creates a black hole
What is the correlation between speed and size of orbit
The smaller the orbit the higher the speed need to be for it to be stable since the force of gravity is stronger the closer you are you need higher speed to maintain your orbit
Difference between geostationary and polar satellites
Geostationary orbit once per 24hr so they orbit the earth and are always pointing at the same place. They have a high orbit and orbit above the equator. Used for TV and communication
Polar orbit satellites orbit in a shorter amount of time and orbit from pole to pole they have a lower orbit. Used to monitor the earth
How does red shift prove the big bang
Light from other stars seem to be shifted towards the red spectrum meaning that they are moving away from us. Light from further away galaxy are more red shifted meaning they are moving away even faster so the unnerves is expanding meaning it had to start from a certain spot and expand out wards this is called big bang theory
Role of dark matter and dark energy in big bang theory
The universe should slow down its expansion because of gravity but it is speeding up its expansion it is suggested dark matter and dark energy which cannot be detected is the cause of this
What is CMBR
Microwave radiation that is in the whole universe believed the gamma radiation from the big bang has been stretched into microwaves
What is a period of wave
The amount of time for a full cycle of wave to pass
Describe water tank required practice
A tank of water 4 cm deep and a piece of white paper underneath and a lamp above. A vibrating bar creates waves in the water by placing a ruler on the paper you can measure the wavelength of 10 waves and then 1 wave can also use a camera to help. For frequency you can count the number of waves passing a point in 10 seconds and divide by 10.
Describe sting wave RP
Attach one end of a string to a vibration generator and the other end to a hook with weights on it pass the string over a pulley. Turn on the vibration generator and change the frequency until a clear wave is visible. You can use a ruler to measure the wavelength each crest being half a wavelength and you know the frequency through the vibration generator
Give names of EM spectrum
Radio waves, Micro waves, infra red, visible light, ultra violet, x-ray, gamma ray
Describe refraction in terms of density
If density is higher when changing material it means the wave slows down making it bend towards the normal so the angle of incidence is more than angle of refraction
If density is less it bends away from the normal so angle of incidence is less than angle of refraction
Different types of radio waves
Long wave radio bends around the earth and can detract (bend) through stuff so it has a long range
Short wave radio reflects of the ionosphere so has a long range
Different uses of EM waves
Microwaves used to heat up food
Microwaves for satellite communication
Infrared for viewing the temperature of objects
Visible light for optic fibre
Ultra violet suntan
X-ray imagery of bones
Gamma rays medical tracer
Difference between real and virtual image
Real image is where all the light rays converge creating an image on a screen
Virtual image is when the light rays are diverging so you look at where the light rays seem to come from
Hoe does distance from lens effect image
If object at 2F the image is inverted, real, same size
If between F and 2F it is inverted, real, bigger
If object is past F the object is right way up, virtual, bigger
How do magnifying glasses work
Use convex lens, the image is closer than F so it creates a virtual, bigger, right way up image for the eye
What does it mean to transmit light
Transparent objects transmit light because they let light through and don’t absorb or reflect all the light
Describe infrared RP
Place a Leslie cube on a heat proof mat and add boiling water.
Wait for it to heat up, place a thermometer on all of its side and they will give the same value.
Hold an infrared thermometer at a set distance(10 cm) form on side of the cube and take a reading. Do the same for the other sides.
Repeat and calculate mean you should find that the black surfaces give out more infrared than the white surface and that matte surfaces give out more infrared than shiny surface
Why is light emitted from hot objects
Every object emits EM waves because of it temperature normal objects emit infrared but when it gets hotter the wavelength changes and so does the intensity of the EM wave
It eventually produces visible light form red hot to white hot to blue hot
What is a perfect black body
Absorbs all the radiation that hits it so no radiation is reflected or transmitted
It can also emit all of it radiation
