Karteikarten
Physics P3 Fashcards
Karten in diesem Stapel (58)
- 1What do we use X-rays in hospitals for?to make images and C.T. scans
to destroy tumours at or near the body surface - 2Why are X-rays dangerous?they ionise substances they pass through, which can damage them.
- 3What can we say about the absorption of X-rays when they pass through the body?X-rays are absorbed more by bones and teeth than by soft tissues
- 4What is a C.T. scan?C.T. scans distinguish between different types of soft tissue as well as bones and teeth
- 5What are ultrasound waves?sound waves of a frequency above 20 000 Hz
- 6What are ultrasound waves used for in medicine?Ultrasonic scanning
Destruction of kidney stones - 7Why is an ultrasound scan safer than a X-ray?It is non-ionising.
- 8What do we mean by the refractive index of a transparent substance?It is a measure of how much a substance can refract a light ray
- 9How can we calculate the refractive index?sin (i)
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sin (r) - 10What do we mean by the critical angle of a substance?the angle of incidence of a light ray in a transparent substance that produces refraction along a boundary
- 11How is the critical angle related to the refractive index of the substance?1
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Sin (c) - 12What do we mean by total internal reflection?when the angle of incidence is greater than the critical angle.
- 13What do doctors use an endoscope for?to see inside the body directly
- 14What is a converging lens?Convex- focuses parallel rays to a point (principal focus)
- 15What is a diverging lens?Concave- makes parallel rays spread out as if they came from a principle focus.
- 16What is a real image?Is formed if the the object is further away than the principal focus
- 17What is a virtual image?Formed if the object is nearer to the lens than the principal focus
- 18What do we mean by magnification?image height
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object height - 19How can we find the position and nature of an image formed by a lens?a ray diagram can be drawn
- 20How does the eye work?Light is focused on to the retina by the cornea and the eye lens, which is a variable focus lens
- 21What is the range of vision of the human eye?25 cm to infinity
- 22What do we mean by the power of a lens?P=1/focal length in meters (f)
- 23What is short sight and how do we correct it?Can only see near objects clearly.
Use a diverging lens - 24What is long sight and how do we fix it?Can only see distant objects clearly
Use a converging lens - 25Why is the refractive index of glass important in making spectacle lenses?The higher the refractive index the thinner and flatter the lens can be
- 26what does the moment of a force measure?The turning affect of the force of an object
- 27How do we calculate the moment of a force?F about a pivot = F x d
were d is the perpendicular distance from the line of action of the force to the pivot. - 28How can we increase the moment of a force?increase f or increase d
- 29What is the centre of mass of an object?Were mass may be thought to be concentrated
- 30What can we say about the centre of mass of an object that is suspended from a fixed point?When it is suspended in equilibrium it's centre of mass is directly below the point of suspension
- 31What can we say about the centre of mass of a symmetrical object?Th centre of mass is along the axis of symmetry.
- 32If an object is in equilibrium the sum of the anticlockwise movements about any point equal...?the sum of any clockwise movement about a point
- 33What can be done to increase the stability of an object?increase the base width and lower the centre of mass
- 34What will make a body topple over?if the line of action is outside it's base
- 35An object topples over if...?the resultant moment about i's turning point is not zero
- 36What do we mean by pressure?It is force divided by the area on which the force acts (pascal (Pa))
- 37What can we say about the pressure in a liquid?it acts equally in all directions
- 38How is pressure transmitted in a hydraulic system?Liquid is virtually incompressible, so the pressure in a hydraulics system is transmitted through the oil
- 39What is centripetal force?An object moving in a circle is acted on by centripetal force
- 40What affects the time period of a pendulum?It's length
- 41How do you measure the time period of a pendulum accurately?Measure the average time for 20 oscillations and divide it by 20
- 42What do we mean by magnetic field lines?The line along which a plotting compass points
- 43How do we make electromagnets?A coil of insulated wire wrapped round an iron core
- 44What are electromagnets used for?scrapyard cranes circuit breakers electric bells relays
- 45What is the motor effect?a force can act on a wire in a magnetic field when we pass a current through the wire
- 46In the motor effect the force is...?-increased if the current of magnetic field strength is increased
-at right angle to the direction of the magnetic field
-is reversed if the current of magnetic field strength is reversed - 47How is the motor effect used to make objects move?an electric motor has a coil which turns when a current is passed through it
- 48What is electromagnetic induction?the process of creating potential difference using a magnetic field
- 49how can a magnet be used to induce potential difference across the ends of the conductor?If a conductor cuts the line of a magnetic field a potential difference is induced across the ends of the conductor
- 50How can potential difference be induced if a electromagnet is used instead of a magnet?It has to be turned on to induce a potential difference
- 51Why do transformers only work with ac?because a changing magnetic field is nececssary to induce ac in the secondary coil
- 52What is the core of a transformer made from?an iron ore unless it is a switch mode transformer which has a ferrite core
- 53How does a switch mode transformer differ from an ordinary transformer?it is lighter and smaller
it operates on a high frequency - 54Why are transformers used on the national grid?to step potential difference up or down
- 55What is the transformer equation?
- 56What is the difference between a step down and step up transformer?for a step up transformer N s is less than N p
For a step up transformer N s is greater than N p - 57What can we say about a transformer which is 100% efficient?Vp*Ip =Vs*Is
where
Ip=primary current
Is=secondary current - 58How do we use physics in hospitals?We use physics whenever:
blood pressure or temp. is measured
ECG recordings are taken
endoscopes are used
scanners are used
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- Finished P3 3.6/3.6 complete flashcard deck for P3 physics
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- Holly Bamford
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