P3 Flashcards
How does ultrasound waves in the bodywork
Ultra waves can pass through the body but whenever they reach a boundary with two different media and like the fluid in the womb and the skin of the fetus, some of the waves is refracted back and detected
What could ultrasound wave be used for
They can be used to break kidney stones which are hard masses that can get blocked. The beam concentrates high energy waves at the kidney stones and turns it into smaller particles
Which out of the three is the most safest to use
Ultrasound waves, x-rays, CT scan
Ultrasound waves are the most safest because there are non ionising
X-rays are ionising and can cause cancer
CT scan is the most unsafeness because it uses more radiation than x-ray so patients are exposed to even more ionising radiation
What is refraction index causes by
Reflection index is caused by the waves changing direction as they enter a different medium this is caused by a change in density from one medium to another which changes the speed of the waves
What formula is used to work out the refractive index
Sin r \ sin I
What is a converging lens
And what does it cause parallel rays of light to do
Converging lens are complex which means it is it’s Thickest in the centre
It causes parallel rays of light to meet together at the principal focus. Rays of light are reflected in words and meet at the focus
What is the principal focus of a converging lens
The principal focus of converging lens is where raise hit in the lens parallel to the axes all meet
What is a diverging lens
What does it cause the parallel rays of light to do
They diverging lens or concave this means it Caves in wards
It causes parallel rays of light to spread out(diverge) and virtual images are form
What is the principal focus of diverging lens
This is the point where on rays hitting the lens parallel to the axes are pairs to all come from – you can trace them back where it will appear to meet up at a point behind the lens
What are the three rules for a refraction in converging lens
incident rays parallel to the axes refracts through the lens and passes through the principal focus on the other side
An incident Ray passing through the principal focus with racks through the lens and travels parallel to the axes
An incident Ray passing through the centre of the lens comes on in the same direction
What are the three rules of a refraction in diverging lens
The incident ray are parallel to the axes through the lens and travel in line with the principal focus
The incident rays passing through the lens towards the principal focus refracts through the lens and travels parallel to the axes
An incident Ray passing through the centre of the lens carries on in the same direction
Define what is meant by a focal length
The distance from the centre of the lens to the principal focus
Define what is meant by a real image
Light from an object comes together to form an image on a screen
Define a virtual image
This is when the rays are diverging so the light from the object appears to be coming from a completely different place
What type of lens is a magnifying glass
Magnifying glasses uses converging lens and it works by creating a magnified virtual image
How does a magnifying glass work
The object is been magnified so must be closer to the lens than the focal length. Since the image produced is a virtual image the light rays don’t actually come from the place where the image appears to be
What is the formula to find out the magnification
Image height divided by object height
If a Lens is very powerful
Describe the focal length
The more powerful the lens, the more strongly it converges rays of light, the shorter the focal length
Converging lens the power is positive
Diverging is the power is negative
What two factors affect the focal length
Refractive index of the lens material
Powerful lenses can be thinner by using materials with a high reflective index
curvature of the 2surfaces of the lens
Strongly curved surfaces makes a more powerful lens
Explain the function of the lens
The lens changes shape to focus light from an object at varying distances. It is connected to the ciliary muscles by the sensory ligament and when the ciliary muscles contract tension is released and the lens take on a fat more spherical shape
When disagree muscles relax the sensory ligaments Pulls the lens into a thinner and flatter shape
What is shortsighted people corrected with
to correct short sightedness you need to put a diverging lens with a negative power in front of a eye
This diverges the light before it enters the eye which means the lens can focus on the retina
What is long sighted people corrected with
To correct longsight a converging lens with a positive power can be put in front of the eye. The light is the refracted and start to converge before it enters the eyes and that image can be focused on the retina where it belongs
How can a laser be used to correct Eye problems
Laser can be used to vaporise some of cornea to change its shape and focusing ability
it can increase or decrease power of the Cornea so that Eye can focus on images properly
What are optical fibres
How do they work
Optical fibres can carry visible light over a long distance
They work by bouncing ways of the side of a thin inner core of glass or plastic. The waves enters one end of the fibre and is reflected repeatedly until it emerges at the other end
How can total internal reflection happen with optical fibres
It can only happen when a wave travels through a dense substance like glass of water towards a less dense substance like air
How is an endoscope used
Endoscopes uses bundles of optical fibres
It consist of two bundles of optical fibres one to carry light to the area of interest and one to carry an image back so it can be viewed
What is it a moment?
A moment is a turning effect of a force
Where can you find the centre of mass
The centre of mass and is directly below the point of suspension
How do you work out if the moment are you equal
Total anti clockwise moments = total clockwise moments
What are levers used for
Levers use the idea of balance moment to make it easier for us to do the work
How does levers work
The moment is equal to the force X distance from the pivot . So the amount of force needed to produce a particular moment depends on the distance the force is applied from the pivot
Levers increase the distance from the pivot at which the force is applied so this means less force is needed to get the same moment
Why levers known as the force multipliers
This is because they reduced the amount of force that is needed to get the same moment by increasing the distance
Examples of simple levels as force multipliers
Wheelbarrows and scissors
What happens if the total anticlockwise moments do not equal the total clockwise moment
There will be in resultant moment so the object will turn
Why are low and wide objects the most stable
This is because they have a wide base and a low centre of mass
Why is it that that unstable objects tips over easily
This is because its centre of mass music be on the edge of it base. Moments- if the line of action of the weight of the object lights outside the base of the object it will cause a resultant mass .this will tip the object over
How is a pendulum made
It is made by a suspending a weight from a piece of string. When you pull back a pendulums and let it go, it will swing back and forth.
Define what I mean by time period
The time taken from the pendulum to swing from one side to the other and back again
How to calculate the time period
1 / frequency
What affects the time period of the pendulums swing
It depends on its length. The longer the pendulum, the greater the time period. So the shorter the level of the shorter the time period
What are x-rays
X-rays are high-frequency, short wavelength electromagnetic waves.
What to materials do x-rays absorb
They are transmitted by healthy tissues but are absorbed by denser material is like bones are metals
X-rays images can be formed electronically using charge – coupled devices
What does charge – couple devices mean
They are silicon chips and can detect x-rays and produce electronic signals which are used to form a high resolution images
How are CT scan formed?
The patient is put inside the cylindrical scanner and then a x-ray beam is filed fruit to body for an x-ray tube and pick up my detectors on the opposite side. The detectors and x-ray tube are rotated during the scan. A computer interprets the signal from the detector to form an image of a two dimensional slice
How can x-rays be used to treat cancer
X-rays can cause ionisation – high doses of x-rays will kill living cells therefore can be used to treat cancer. The x-rays all focused on the tumour or using a wide beam. The beam is rotated round the patient with the tumour at the centre.this minimises the exposure of normal cells to radiation, and reduces the chances of damage and the rest of the body
how do you radiographers to work with x-ray machines and CT scanners need to take precaution to minimise their x-ray does
They were lead apron and stand behind a lead screen all leave the room while scans Are being done
Lead is used to shield areas of the patient body that aren’t been scanned and exposure time to the x-rays is always kept to an absolute minimum
Describe the pressure in a liquid
The pressure in a liquid is all transmitted equally in all direction
What are hydraulic systems
They are force multipliers which use a small force to product a bigger force h
Describe the velocity in an object that is travelling in a circle
What is the centripetal force
It’s constantly changing direction , this means the velocity is constantly changing so the object acceleration changed the direction of motion but not the speed. The acceleration is towards the centre of the circle . There must be a resultant force acting on the objects causing this acceleration .
The centripetal force is the force that keeps something moving in a circle
What type of force is actually proving the centripetal force in a given situation
Friction- a car going round a bend - friction between the cars tyre and the road
Tensions - a bucket whirling round on a rope & a spinning fairground ride
What does centripetal force depends on
Mass
Speed
Radius
What are the three things that mean you need a bigger centripetal force ?
More speed
More mass
Smaller radius of circle
Define a magnetic field
A regions where magnetic materials like iron and steel and also wires carrying current experience a force acting on them
Explain the magnetic field round a current carrying wire
When a current flows through a wire a magnetic field is created around the wire
The field is made up of concentric circles with the wires in the centre
Explain the magnetic fields round a coil of wire
The magnetic field inside a coil of wire ( a solenoid )
Outside the cool the magnetic field is just like one round a bar magnet
If you stop the current , the magnetic field disappears
What are electromagnet
A magnet whose magnetic field can be turned on and off with an electric current
How can you increase the magnetic field around a solenoid
By adding magnetically soft iron core through the middle of the coil
Example of electromagnetic use
Cranes
What is a motor effect
The force experienced by a current wire in a magnetic field
2 factors which speed up the simple electric motor
More current
Stronger magnetic field
What is an electromagnetic induction?
The creation of a potential difference across a conductor which is experiencing a change in magnetic field
Examples of where electric motor are used in
CD players
Food mixers
Fan heaters
Some appliances use electromagnetic induction to generate a current
How are dynamos used
Dynamos are often used on bikes to power the lights. The cogwheels at the top if positioned so that it touching one of the wheels. As the world move round, it turns the cold which is attached to the magnet. This creates an AC current to power the light
What are transformers
Transformers use electromagnetic induction to change the potential difference. They only work on ac
What are step up transformers
Step up transformers increase the voltage. So they have more turns on the second coil than the primary coil
What are stepdown transformers
They decrease the voltage down. They have no turns on the primary coil done the secondary coil
How does transformers work by electromagnetic induction
The primary coil produces a magnetic field which stays within the iron core
Because there is an alternating-current in the primary coil, The field in the iron core is constantly changing direction
This rapidly changing magnetic field is them felt by the secondary coil
The changing Field induces an Alternating potential difference across the secondary coil
The relative number of turns on the 2 coils determine whether the potential difference induced in the secondary coil is greater or less than the potential difference in the primary
What are Switch mode transformers
They are a type transformers that operate at a higher frequency than the traditional Transformers
This makes them more useful in things like mobile phone charges and power supplies
Why are switch mode transformers more efficient than other type of transformers
There is very little power when they are switched on but no load
What is the job of the retinal
This is where images of fault it is covered in light-sensitive cells. These cells detect light and send signals to the brain to be interpreted
What is the iris
This is the coloured part of the eye it is made up of muscles that control the size of the pupil. The hole in the middle of the erase controls the intensity of light entering the eye
What is the job and the function and the function of a cornea
It is a transparent window with a convex shape and has a high reflective index. Does most of the eyes focusing
What is meant by hydraulic system being used as force multipliers
They use a small force to produce a bigger force . They do this using liquid and with the cross sectional area
How does a simple hydraulic system work
The system has to piston one with a smaller cross-sectional area then the otherpressure is transmitted equally through a liquid so the pressure at both pissed and is the same.
Pressure = force\area so at the 1st piston a pressure is exerted on the liquid using a small force over a small area. The pressure is transmitted to the 2nd piston
The 2nd piston has a larger area and so as Pressure = force\area there will be a larger force
