Fichas
Physics Unit 3
Fichas del conjunto (64)
- 1State the properties of X rays.• X rays have short wavelength (around
the same as the diameter of an atom).
• X rays are ionising.
• X rays pass through soft tissue but are
absorbed by metal and bone.
• X rays affect a photographic film the
same way as light. - 2Describe how X rays can be used to diagnose and treat medical conditions.CT scans use X rays to diagnose
tumours. Dental X rays diagnose
dental problems. Charge-coupled
devices allow X ray images to be
analysed electronically. X rays can
be used to kill cancer cells. - 3State the precautions necessary when X ray machines and CT scanners are used.X rays are ionising and mutate DNA,
increasing the risk of cancer. We need
to minimise exposure to X rays (eg
limit the number of X ray scans a
patient can have in a year, ensure that
X ray technicians are protected with
lead screens etc). - 4What is meant by ultrasound?Ultrasound is sound waves
which have a higher frequency
than humans can hear (greater
than 20,000 Hz). - 5How are ultrasound waves used to visualise internal structures?Ultrasound waves are reflected at
density boundaries (eg between
soft tissue and bone). The time
taken for reflection can be used to
calculate distance from the
ultrasound probe. - 6State two examples of the use of ultrasound in medicine.Ultrasound is used to scan
pregnant women to check the
health of a foetus. It can also be
used to break up kidney stones so
they can be passed out of the body. - 7State an advantage and disadvantage of ultrasound.Ultrasound is safe as it is not
ionising. However, it produces
low-resolution images. - 8What is meant by refraction?Refraction is the change in
direction of light when it
passes from one medium to
another (slows down or
speeds up). - 9What is meant by the principal focus of a lens?Parallel rays of light are brought
to a focus at the principal focus.
The distance from the lens to the
principal focus is called the focal
length (F). - 10State the nature of an image produced from a convex (converging) lens when the object is closer than the focal length.With a convex (converging) lens,
when the object is closer than
the focal length, the image is
magnified, upright and virtual.
This is a magnifying glass. - 11State the nature of an image produced from a convex (converging) lens when the object is at the focal length.With a convex (converging)
lens, when the object is at the
focal length, there is no image. - 12State the nature of an image produced from a convex (converging) lens when the object is between the focal length (F) and twice the focal length (2F).With a convex (converging) lens
when the object is between the
focal length (F) and twice the focal
length (2F), the image is magnified,
inverted (upside down) and real. - 13State the nature of an image produced from a convex (converging) lens when the object is at twice the focal length (2F).With a convex (converging) lens
when the object is at twice the focal
length (2F), the image is the same
size as the object, inverted (upside
down) and real. - 14State the nature of an image produced from a convex (converging) lens when the object is further than twice the focal length (2F).With a convex (converging) lens
when the object is further than
twice the focal length (2F), the
image is smaller than the object,
inverted (upside down) and real. - 15What can we say about the image produced by a concave (diverging) lens?The image produced by a concave
(diverging) lens is always upright,
diminished (smaller than the object)
and virtual. The image is also on the
same side of the lens as the object. - 16What is the equation to calculate the magnification produced by a lens?
- 17In the eye, what is the function of the retina?The retina contains lightsensitive
cells
(photoreceptors). The light is
focused here and electrical
impulses are sent to the brain. - 18In the eye, what is the function of the lens.The lens carries out the final
stage of focussing the light onto
the retina. The shape of the lens
can be adjusted to focus on near
or distant objects. - 19In the eye, what is the function of the cornea?The cornea is the transparent
front of the eye. Light rays are
partially focused as they pass
through the cornea. - 20In the eye, what is the function of the pupil/iris.The pupil and iris work
together to control the intensity
of the light pass into the eye. If
the light is too bright, the iris
makes the pupil smaller. - 21In the eye, what is the function of the ciliary muscle?The ciliary muscle contracts or
relaxes to control the shape of
the lens during focusing. - 22In the eye, what is the function of the suspensory ligaments?The suspensory ligaments
attach the lens to the ciliary
muscle. - 23What is the range of vision of the human eye?The range of vision is between
25cm (the near point) and
infinity (the far point). - 24What is meant by long sight? How is this corrected?In long sight, the eyeball is too short,
or the lens is unable to focus the light
strongly enough. This means that the
light is focused behind the retina. This
is corrected using a convex
(converging) lens. - 25What is meant by short sight? How is this corrected?In short sight, the eyeball is too long,
or the lens focuses the light too strongly. This means that the light is focused in front of the retina. This is corrected using a concave (diverging) lens. - 26In a camera, what is the equivalent of the retina in the eye?In a camera, the film (or the
charge-coupled device) is the
equivalent of the retina in the
eye. - 27How do we calculate the power of a lens?The unit of power is the dioptre (D)
- 28What can we say about the power of a converging lens and a diverging lens?The power of a converging
lens is positive. The power of a
diverging lens is negative. - 29What two factors determine the focal length of a lens?The focal length of a lens is
determined by the refractive
index of the material and the
curvature of the two surfaces
of the lens. - 30Why are lenses made of a high refractive index material so useful?Lenses with a high refractive
index can be manufactured
thinner. So for example,
glasses can have thinner,
lighter lenses. - 31How do we calculate the refractive index of a material?
- 32What is meant by total internal reflection.If a beam of light strikes a
boundary at greater than the
critical angle, the beam
reflects back into the medium.
This is used in optical fibres. - 33State an example of total internal reflection in medicine.Total internal reflection is used
in endoscopes to look inside
the body. - 34State an example of total internal reflection in technology.Total internal reflection is used
to send broadband signals
down optical fibres to homes
and businesses. - 35Describe a medical use for lasers.Lasers are used in laser eye
surgery to correct vision
defects. They can also be
used to cauterise (seal) a
wound. - 36What is meant by the centre of mass of an object?The centre of mass of an
object is the point at which the
mass may be thought to be
concentrated. - 37How can we determine the centre of mass of an object.Allow the object to hang from a pin.
Use a weight on a string (plumline)
to draw a vertical line down the
object. Reposition the object and
repeat. Where the two lines cross is
the centre of mass. - 38What is meant by the time period of a pendulum.The time period of a pendulum
is the time taken to swing from
one side to the other and back
again. - 39How do we calculate the time period for a pendulum?T = time period (s)
f = frequency (Hz)
- 40Which type of objects are most stable (less likely to topple)?Objects which are more stable
have a wide base and a low
centre of mass (such as a gokart). - 41What does the time period of a pendulum depend on?The time period of a pendulum
is only dependent on the
length of the pendulum. - 42What do we call the turning effect of a force?The turning effect of a force is
called the moment. - 43How do we calculate the size of a moment?Moment (Nm) = force (N) x distance (m)
- 44What is the unit of moment?The unit of moment is Nm
(Newton Metre) - 45If an object (eg a seesaw) is not turning, what can we say about the moments?If an object is not turning then
the total clockwise moment is
balanced by the total
anticlockwise moment. - 46Why do objects topple?An object topples if the line of
action of the weight lies
outside the base of the object.
This will result in a moment. - 47What can we say about pressure in a liquid?Liquids are virtually
incompressible. This means
that the pressure in a liquid is
transmitted in all directions. - 48How do we calculate the pressure in a hydraulic system?P = pressure (Pa)
F = force (N)
A = cross-sectional area (m sq)
- 49In circular motion, where is the direction of acceleration?In circular motion, the direction
of acceleration is towards the
centre of the circle. - 50In circular motion, what is the effect of the acceleration?In circular motion, the effect of
the acceleration is to change
the direction but not the speed
of the object. - 51What do we call the resultant force causing the acceleration in circular motion?In circular motion, the resultant
force causing the acceleration
is called the centripetal force. - 52What is the direction of centripetal force in circular motion?When a current flows through
a wire, a magnetic field is
produced around the wire. - 53State three ways we can increase the centripetal force needed to make an object perform circular motion.We can increase the centripetal force
needed to make an object perform
circular motion by:
• Increasing the mass of the object
• Increasing the speed of the object
• Decreasing the radius of the circle - 54What happens when a current flows through a wire?If a current-carrying wire is
parallel to a magnetic field, it
will not experience a force. - 55State two ways that we can increase the force experienced by a current-carrying wire placed in a magnetic field.We can increase the force
experienced by a current-carrying
wire placed in a magnetic field by
increasing the strength of the
magnetic field or increasing the
size of the current. - 56If a current-carrying wire is parallel to a magnetic field, what can we say about the force?If a current-carrying wire is
parallel to a magnetic field, it
will not experience a force. - 57In Fleming’s left hand rule, what is shown by: • The first finger • The second finger • The thumbIn Fleming’s left hand rule,
• The first finger = field (N to S)
• The second finger = current (+ to -)
• The thumb = direction of motion - 58How does a transformer work?In a transformer, an alternating current
in the primary coil produces a
changing magnetic field in the
secondary coil. An alternating potential
difference is induced across the ends
of the secondary coil. - 59What is the purpose of a stepup transformer?In a step-up transformer, the
potential difference across the
secondary coil is greater than
that across the primary coil. - 60What is the purpose of a stepdown transformer?In a step-down transformer,
the potential difference across
the secondary coil is less than
that across the primary coil. - 61What is the transformer equation?
- 62What can we say about the power input and output for a transformer?If a transformer is 100% efficient,
the output power would be equal
to the input power. However,
remember that transformers are
never 100% efficient. - 63What is the operating frequency of a switch-mode transformer?Switch-mode transformers
work at a very high frequency
(50,000 Hz - 200,000 Hz). - 64What are the advantages of a switch-mode transformer compared to a traditional 50 Hz transformer?Switch-mode transformers are
much lighter and smaller than
traditional transformers. They also
use very little power if they are
switched on but no load is applied.
Información
- Descripción
- GCSE Physics Fichas sobre Physics Unit 3, creado por Rick Wear el 13/04/2017.
- Creado por
- Rick Wear
- Visitas
- 0
- Etiquetas
- Valoración