Physics Theory Flashcards
What are longitudinal waves?
When the vibrations move in the same direction as the energy travels in e.g. sound waves
What are transverse waves?
When the vibrations move at right angles to the direction the energy travels in e.g. visible light, EM spectrum
Do long wavelengths or short wavelengths diffract more?
Long wavelengths diffract (bend) more than short wavelengths
Do waves diffract more through a narrow gap or wider gap?
Waves diffract more through a narrow gap
List the waves of the EM spectrum in order?
Gamma rays, X-rays, Ultraviolet, Visible Light, Infrared, Microwaves, Radiowaves
What do all the waves in the EM Spectrum have in common?
-Travel at the speed of light
-Can travel through a vacuum
-Can be reflected
-Can be refracted
-Can be diffracted
List the colours of the visible spectrum from highest wavelength to lowest
red. orange, yellow, green, blue, indigo, violet
(ROYGBIV)
Define the particles in an atom
Proton: postive, mass=1, located in the nucleus
Electron: negative, mass= near 0, orbits the nucleus
Neutron: charge is 0, mass=1, located at the nucleus
Define Ionisation
The process of adding or removing electrons
Define Ionising Radiation
Materials that can cause ionisation in other atoms
Define the radiation type ‘Alpha’
Symbol: α
It is a Helium nucleus
Highly ionising
Absorbed by air or paper
Define the radiation type ‘Beta’
Symbol: β
It is a fast electron
Less ionising than alpha more than gamma
Absorbed by mms of aluminium
Define the radiation type ‘Gamma’
Symbol: γ
It is a high energy wave in the Em Spectrum
Not very ionising
Absorbed by a few cms of lead
What are the types of natural background radiation?
-Radan Gas
-Cosmic rays from the sun and outer space
-Rocks and Soil
-Foods (e.g. banana)
-The Human body
What are the types of artificial background radiation?
-Medical sources, e.g. x-rays
-Fall out from weapon testing
-Nuclear Power stations
-Radioactive waste
Describe the Half-Life Experiment
- To ensure a fair test measure the background radiation
- Use a geiger muller tube to count the number of decays from a source in a minute. Take away from the background radiation count
- Calculate activity over the minute (A=N/t)
- Repeat process at regular intervals
- Plot activity (y-axis) against time (x-axis)
- Use graph to find half life
What does the risk of biological harm from exposure to radiation depend on?
-The Absorbed dose
-The type of radiation (alpha, beta, gamma)
-The body/organs/tissue exposed
Define Nuclear Fission
The splitting of a large and unstable nuclei, into 2 more stable nuclei, neutrons whilst energy is released
Define a chain reaction during Nuclear Fission
When the neutrons produced by the fission reaction can then go on to further reactions
Define Nuclear Fusion
When 2 light nuclei combine to make a bigger nucleus, producing extra energy
Why is Nuclear Fusion mostly impossible on Earth?
-Fusion is how stars produce their energy
-It is difficult (close to impossible) to do on Earth for electricity production
-This is because fusion requires high temperatures and and abundance of light elements are required
What are the Pros of Nuclear Power?
-Clean: doesn’t produce CO2 and greenhouse gases
-Little fuel is required to produce a lot of energy
What are the cons of nuclear power?
-Non-renewable energy source
-A serious accident in a nuclear power station is a major disaster
-Nuclear power stations produce radioactive waste, some of which is very difficult to deal with
-After a few decades nuclear power stations themselves will have to be disposed of
What are the ways to keep safe around nuclear radiation?
-Use forceps to pick up source
-No contact with skin
-Protective clothing e.g. lead apron
-Limit time with source
-Point away from the body
What is the experiment for Instantaneous speed?
- Measure the distance, d, with a ruler, metre stick or trundle wheel.
- Measure the time taken, t, with a stop clock.
- Calculate the instantaneous speed by dividing the distance travelled by the time taken.
List examples of vectors
velocity
displacement
acceleration
force
momentum
List examples of scalars
speed
distance
time
mass
energy
What is Newtons First Law?
An object will stay at rest or keep moving in a straight line at a constant speed if balanced forces are acting on it
What is Newtons Second Law?
Unbalanced Force=mass x acceleration
What is Newtons Third Law?
Every action has an equal and opposite reaction
What is a satellite
-They are objects that orbit a planet
-They can be natural e.g. the moon
-They can be man-made e.g. international space station
-The larger the height the longer the orbital period
Define a Geostationary Satellite
-A satellite that remains above the same point of the Earths Surface
-Has an orbital period of 24hrs
-They orbit Earth 36,000km above the Earths surface and are used for telecommuncations
What happens during Re-entry?
When the spacecraft enters the Earth’s atmosphere there is an energy change: Kinetic to Heat
This is due to the friction between the particles in the atmosphere and the outer surface of the space shuttle rumbling against eachother
How can we counteract the large energy transfer during Re-entry?
-Silica tiles are used to protect from the heat. The tiles are painted black so that heat is lost to the surroundings
-This is commonly known as a heat shield
What is the Big Bang Theory?
-Scientists estimate the age of the universe to be 13.8 billion years old
-The universe seems to be expanding from a single point
-Scientists don’t have any firm evidence that the Big Bang Theory actually happened
What is the evidence that supports the Big Bang Theory
-Red shift and expanding universe
-Abundance of light elements
-Cosmic microwave background radiation
What is the law of conservation of energy?
Energy cannot be created or destroyed. It can only be changed from one form to the other.
Define Potential Difference
This is the energy given to each coulomb of charge passing through the supply
Define Direct Current (DC)
The flow of electrons through a circuit are in one direction only.
e.g. batteries, electronic equipment, solar cells
Define Alternating Current
The flow of charge (electrons) regularly reverses its direction through the circuit with time.
What happens to a transistor when it’s dark
-As the light level of the LDR decreases the resistance of the LDR increases
-This means the voltage of the LDR will increase also
-When this voltage over the LDR reaches a certain value, the transistor will conduct
-Current will flow to the bulb and switch it on
What happens to a transistor when it’s light
-As the light level of teh LDR increases the resistance of the LDR decreases
-This means the voltage of the LDR will decrease also
-The Voltage over the V2 will therefore increase
-When this voltage over the resistor reaches a certain value, the transistor will conduct
-Current will flow to the bulb and switch it on
What happens to a transistor when it’s cold
-As the temperature of the thermisor decreases the resistance of the thermistor will increase
-This means the voltage of the thermistorwill increase also
-When this voltage over the thermisor reaches a certain value, the transistor will conduct
-Current will flow to the bulb and switch it on
What happens to a transistor when it’s hot
-As the temperature of the thermistor increases the resistance of the thermistor decreases
-This means the voltage of the thermistor will decrease also
-The voltage over the resistor will therefore increase
-When the voltage over the resistor reaches a certain value, the transistor will conduct
-Current will flow to the bulb and switch it on
If the power is below 700W then what fuse can be used?
3A fuse
If the power rating is above 700W then what fuse can be used?
13A fuse
What would happen to the pressure if the volume of an object decreases?
-If the volume of a container decreases the particles collide with the walls more often.
-This causes the force to increase therefore the pressure increases.
What would happen to the pressure if the volume of an object were to increase?
-If the volume of a an object were to increase the particles collide with the wall more often.
-This causes the force to decrease therefore the pressure to decrease.
Formula for converting from Celsius to Kelvin
+273
Formula for converting from Kelvin to Celsius
-273
How are pressure and volume related?
Inversely proportional (when on value increases the other value decreases)
How are pressure and temperature related?
Directly proportional (both values increase or decrease)
What happens to the pressure of an object if the temperature increases (fixed volume)
-If a gas at fixed volume is heated the particles will gain kinetic energy which will make them move faster.
-This means they will collide with the walls more frequently
-This causes the force acting on the walls of the object to increase and so the pressure increases.
What happens to the pressure of an object with a fixed volume if the temperature decreases?
-If a gas at a fixed volume is cooled the particles will lose kinetic energy which will make them move slower
-This means they will collide with the walls less frequently
-This causes the force acting on the walls of the the object to decrease and so the pressure decreases.
What would happen to the volume of an object with a fixed pressure if the temperature is increased?
-The higher the temperature the more kinetic energy the particles have, the faster they move.
-If the pressure is fixed, particles colliding with the walls of the their object exert a force.
-Increasing the size/volume of the object.
What would happen to the volume of an object with a fixed pressure if the temperature is lowered?
-The lower the temperature the less kinetic energy the particles have, the slower they move.
-If the pressure is fixed, particles colliding with the walls of the their object exert a force.
-Increasing the size/volume of the object.
