Physics Higher 4 GCSE Flashcards
What are waves
Vibration of atoms
Longitudinal waves
The direction of the movement of the particles is equal to the direction of the wave
Transverse waves
The direction of the movement of the particles is at 90 degrees to the direction of the wave
Difference between electromagnetic and mechanical waves
Mechanical waves need matter to travel through, but EM waves don’t
What is a time period of a wave
The time it takes for the wave to finish one wave
equation for wave velocity
wave velocity(m/s) = frequency (Hz) * wavelength (m)
How to measure the velocity of sound
You can time how long it takes to hear an echo of a clap when you are at a distance from a wall, you can work out the velocity of the clap too.
OR
You can connect a pair of microphones a certain distance apart to an oscilloscope.
What happens to sound waves when it travels across a boundary
When a wave travels from one medium to another, its velocity can change as well as its direction. This is called rarefaction
What happens to a sound wave at a boundary
the sound can be:
reflected
transmitted
absorbed
what is ultrasound
sound of a frequency higher than 20,000 Hz. This means that we can’t hear it, but other animals can
Uses of ultrasound
In pregnancy scans
Transmitter beams ultrasound into the mother
The waves reflect at different boundaries
The machine calculate using the time and velocity, to produce an image
Can also be used for echo-sounding and sonar
How does an ear work- explanation
As the sound travels to the eardrum, and it vibrates, it makes the ossicles vibrate. They act like levers to amplify the vibration and pass it on to the inner ear through the oval window.
The cochlea contains fluid which transmits the movements of the oval window to small hairs on the inside wall of the cochlea. These hairs are attached to sound-detecting cells that release chemical substances, which sends a signal to the brain using nerves.
EM spectrum
(increasing frequency)
Radio waves, microwaves, infrared, visible light, UV, X-Rays, gamma rays
What wave is an EM wave
a transverse wave
it has oscillating electric field and magnetic fields.
How are radio waves produced and detected
An oscillating pd across a wire makes electrons move back and forth. This produces a changing electric and magnetic field, which is emitted as a radio wave.
When the fields meet another metal, this makes the electrons move, producing an electrical signal. EM waves are also produced by the movement of electrons in atoms
what is the speed of an EM wave
It always travels at 3 * 10 to the power of 8
What is a CCD image
A charge-coupled device
How are gamma rays used for imaging
A doctor injects the patient with a radioactive substance that emits gamma rays.
Ionosphere
High frequency radio waves pass through the ionosphere, but lower frequency ones are reflected.
What is the description of a concave lens
Virtual, diminished, upright
Examples of concave lenses
Spy holes in doors
Back windows of coaches
Examples of convex lenses
Magnifying glass (virtual, magnified, upright)
Camera, Eye (real, diminished, inverted)
Projector (real, magnified, inverted)
Microscope (real, inverted)
When is an image virtual
If it is made on the same side as the actual object
What are the 2 types of reflection
Specular- gives a sharp image
Diffuse- Blurry image
Why do atoms emit radiation
Because they are unstable.
What is alpha radiation
a helium atom’s nucleus
What is beta radiation
a fast moving electron
How can you detect radiation
Using a Geiger counter. A device that clicks when radiation enters it.
What is alpha radiation stopped by
air or paper
What is beta radiation stopped by
Aluminium
What is gamma radiation stopped by
Lead or concrete
What is ionising power
The radiation emitted by radioactive material, meaning that the radiation can remove electrons to form ions
What is the ionising power of all 3 radiation
Alpha: high
Beta: medium
Gamma: low
Calculating with half life
- find the number of half lives in the days ( days/ half life)
- use that to calculate the new activity. (1/2 multiplied by itself the new activity number of times)
- multiply that number by the original activity
What is the absorption spectrum
The set of frequencies of radiation absorbed by an atom when it is excited and the electron moves to a higher shell
What is the emission spectrum
The set of frequencies of radiation emitted by an atom when the electron moves to a lower shell
Nuclear Fission
A larger nucleus splits into fragments and emits neutrons. It needs a neutron to start the reaction. In each splitting, more neutrons are fired out, to continue the chain reaction
Nuclear Fusion
When 2 nuclei join. It requires a lot of energy and pressure, can only be done on the Sun so far.
Releases energy through e= change in mass *speed 2
types of stores
chemical kinetic thermal gravitational nuclear electrostatic magnetic
Thermal conductivity
The lower the thermal conductivity, the less heat it will conduct. So better for walls
how to increase efficiency
use insulation to reduce wasting heat
make devices from materials that reduce unwanted heat transfer
use technologies that are better at their job
when a ball is dropped, how does its energy store change
before: lots of gravity store
after: lots of kinetic store