Physics Flashcards
What is a wave
A transfer of energy from an origin to the desired output
What is amplitude
The height of a wave e.g. zero position to trough
What are the crest and the trough of a wave
Crest= the top of the waves curve
Trough= the bottom of the waves curve
What is wavelength
The distance taken for a wave to repeat itself
What is the zero position of a wave
Where the medium would be without a wave passing through it
What is the medium
The material that a wave travels through
What is the period of a wave
The time taken for a wave to repeat itself
What is the frequency
The number of complete waves per second
What is the formula of frequency
Frequency= No. of waves/ time
How can period be calculated
Period= time/ No. of waves
What are the two types of wave
+ transverse
+ longitudinal
What is a transverse wave
A wave in which the particles of the medium are vibrating perpendicular to the direction of energy transfer. An example of this a light wave
What is a longitudinal wave
A wave in which the particles in the medium are vibrating in the same direction as that of energy transfer.
What can sound waves travel through
Solids, liquids and gases but they can’t travel through a vacuum
Why can’t sound waves travel through vacuums
As the vacuum reduces the pressure of an area and this reduced pressure means that there are larger spaces between particles and the energy can’t be transferred as the particles aren’t colliding.
How can speed, distance or time be measured
V=d/t
What must you remember when solving problems involving reflection
The wave must cover twice the distance as it must get to the reflector and back to the point of origin.
What apparatus can be used to measure the speed of sound
TSA: \+ glass bottle \+ metal rod \+ timer \+ sound activated switches \+ meter rod
What is the speed of sound general recorded as?
340 ms-1
What equation can be used to find frequency, wavelength or speed.
V=fllamda (very fast Lamborghini)
This is known as the wave equation
What is white light
A mixture of colours which can be separated into their wavelength by passing it through a prism. This is known as refraction
What are the colours revealed by refraction known as
Visible light
Revise EM spectrum
Now
What comes after red light, at the end of the visible spectrum.
Infrared light, which is similar to red light. The infrared frequencies nearest visible are called near-infrared.
What comes after violet light, at the end of the visible spectrum
Ultraviolet light
What is acronym for the EM spectrum
Real Men In Velcro Uniforms Xterminating Germs
What do light waves not need
A medium to travel through
What can light waves do that sound waves can’t
Travel through vacuums
What is the speed of light
3x10 to the 8
What can light do when it hits a surface
+ transmit through it
+ get absorbed by
+ reflect off it
What is the ray of light that travels towards the reflection point known as
The incident ray
What is the ray of light travelling away from the reflection point known as
The reflected ray
What is the normal
The perpendicular line to the surface of reflection at that point.
What is the angle of incidence
The angle between the normal and incident ray
What is the angle of reflection
The angle between the normal and the reflected ray.
What is the law of reflection
The fact that the angle of incidence is always equal to the angle of reflection
Why does reflection only work on smooth surfaces
As otherwise the rays are scattered in different angles
What is a concave lens
A lens in which the reflector reflects beams off the inside of a curve
What is a focal point
The point where the reflected rays converge at one place.
What is the focal length
The distance from the reflecting lens to the focal point
What is a convex reflector
A reflector in which the rays bounce off the outside of the curve
What is refraction
The altering of a rays path as it goes through different materials and therefore densities, allowing it to travel at different speeds
What happens when a ray goes from a less to more dense material
The ray bends toward the normal
What happens when a ray goes form a more to less dense material
The ray bends away from the normal
What changes when refraction occurs
Speed, direction and wavelength however frequency never changes
What is a converging lens
A lens which is thickest in the middle and therefore causes the rays to bend towards each other
What is a diverging lens
A lens that is thickest on the outside and therefore causes the rays to bend away from each other
What is total internal reflection
When a light ray meets an internal wall of a transparent material at a large angle of incidence and reflects off it.
What is an example of technology which uses total internal reflection
Optical fibres which then use the energy to carry lots of data
What must happen for total internal reflection to occur
The angle of incidence must be greater than the critical angle
What is diffraction
When waves bend around obstacles or objects
A longer wavelength causes for a greater…
Angle of diffraction
What happens when a wave passes through a gap
It diffracts at both ends, causing it to become circular as the rays bend towards each other
What is loudness of a sound measured in
Decibels and can be measured with a sound level meter
What can the decibel scale be described as
Non-linear
What does this mean
If a sound is ten times louder than another it differs by 10 dB however if it is one hundred times louder than another it differs by 20 dB
What is the human sound frequency range
20 Hz to 20 kHz
What is infrasound
Sound that is lower than 20 Hz
What is ultrasound
Sound that is higher than 20 kHz
What is an unstable nuclei
A nucleus that has too few or too many neutrons compared to origins making it charged.
How does it become stable
Radioactive decay
What are the three types of radioactive decay
+ alpha
+ beta
+ gamma
What does alpha radiation consist of
Two protons and two neutrons
What do beta particles consist of
Fast moving electrons
What does gamma radiation consist of
EM waves with a very high frequency
What is the charge of:
A- alpha
B- beta
C- gamma
A- two positive
B- one negative
C- no charge
What is the range of alpha (A), beta (B) and gamma (C) particles in air
A- 5 cm
B- 10 m
C- almost infinite
What can alpha radiation be absorbed by
A sheet of paper
What can beta particles be absorbed by
3-5 mm of aluminium
What can gamma particles be absorbed by
5 cm of lead
What is the speed of the three types of radiation
Alpha has a speed of 3x10 to the 7 ms-1
Beta has a speed of 2.7x10 to the 8 ms-1
Gamma has a speed of 3x10 to the 8 ms-1
What are ways to prevent radiation exposure
+ distance
+ time
+ shielding
What is ionisation
The gain or loss of an electron from a stable atom
Why does alpha radiation cause electrons to be removed
It attracts them due to its positive charge
Why does beta radiation cause electrons to be removed
It repels them due it similar negative charge
How does gamma radiation cause for electrons to be removed from an atom
They knock them away by bashing into them
How can nuclear radiation be detected
+ a Geiger-muller tube
+ a spark counter
+ a film badge
What is background radiation
The natural radiation already present on earth such as food and drink and gamma rays from the ground.
What is activity
The number of nuclei that decay per second
What formula can be used to calculate activity
A= N/T
What is half life
The time taken for the activity of a substance to half
How can half life be calculated from a graph
By finding a time and recording its activity then finding half of that time and recording its activity, the difference in activity is the half life.
What is an example of a long term effect of radiation exposure
Cancer
What is absorbed dose
The energy absorbed per kilogram of absorbing material . It is measured in grays
How can absorbed dose be calculated
D= E/M
What is equivalent dose
The effect that radiation has in living tissue. It is measured in sieverts
How can equivalent dose be calculated
H= DWr
What is the annual average background radiation in the UK
2.2 msV
What are the two types of basic electrical circuit
Series
Parallel
What is an electrical current
The rate of flow of charge
What must be present for a current to flow
+ a complete conducting path
+ a source of energy
What do electrical conductors do and electrical insulators don’t
Allow electricity to flow through them
How can current be calculated
I= Q/T
What is potential difference and how can it be calculated
The measure of electrical energy given off by one coulomb and can be calculated using the formula V= E/Q
What are charge and potential difference measured with
Charge is measured with an ammeter
Potential difference is measured with a voltmeter
What is the opposition to current
Resistance
What does resistance depend on
Length, thickness and temperature of resistor as well as the material it is made of
What is ohms law
V= IR
CURRENT STAYS THE SAME IN SERIES CIRCUITS
dab
What is resistance measured in
Ohms
In a parallel circuit the branch with the highest resistance…
Will have the lowest split of current
In a series circuit the branch with the highest resistance will have…
The highest share of voltage
What is power
Power is the measure of energy transferred each second
How is power usually calculated
P= E/T
How is power calculated when current and p.d. are known
P= IV
How is power calculated when current and resistance are known
P = Isquared R
How is power calculated when p.d. and resistance are known
P= vsquared/ R
What is a direct current
One which flows in only one direction
What is an alternating current
One that alternates direction and therefore appears to move to and fro on an oscilloscope.
What s the UK mains voltage and frequency
230 V and 50 Hz
What is a potential divider circuit
Two components connected in series, usually resistors
What is the equation to find a the voltage of a branch of a potential divider
V= (R2/R1+R2) x supply voltage
What does the supply voltage do in a potential divider
Divide in proportion to the size of each resistor meaning v1/v2 is equal to r1/r2
What is an LDR and what does LURD mean
A light dependant resistor and as the light level increases the resistance decreases
What is a thermistor and what does TURD mean
A switch dependant on temperature. As the temperature increases the resistance decreases.
What is a protection resistor
One which is in place to prevent fragile components from overheating
What is a transistor and what are the two main types of transistor
A transistor is a circuit that is used as an electrical apswitch and the two main kinds are NPN and MOSFET.
At what voltage does an NPN switch on
0.7 V
At what voltage does a MOSFET switch on
2 V
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