THERMOMETERS

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THERMOMETERS
There are many different types of thermometers
but they all have one thing in common they all
have a property that changes with temperature.
Look at the display of thermometers.

• How do they work?
• What differences are there between the clinical
  thermometer and the lab thermometer?
• How does the doctor use a clinical thermometer?

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THERMOMETERS -answers

• A thermometer must have some physical property
  that changes with temperature e.g. mercury
  expands when heated.

• A clinical thermometer has a small range, a
  kink and a triangular shape.

• Shake thermometer place under tongue for
  60sec remove for reading.

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SOUND
Sounds are produced by vibrations. For a sound to
be transmitted, there must be particles between
the source and receiver. Sounds can travel
through solids, liquids and gases, but not
through a vacuum. The sound wave travels at
340ms-1 through the air. They travel fastest
through solids and slowest through gases.
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SPEED OF SOUND
LEARNING INTENTION
To calculate the speed of sound experimentally. 
APPARATUS
fast timer 2 microphones, metre stick
METHOD
Place the 2 microphones 1m apart. Switch on
timer. Clap hands above start microphone. Record
time in table. Repeat twice more. Calculate
average time using v d/t.
RESULTS
Attempt Time (?s)
1
2
3
Speed of sound equals 340m/s.
CONCLUSION
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STETHOSCOPE
The stethoscope is used in medicine to listen to
heart and lung sounds. The large closed bell is
used to listen to high frequency lung sounds and
the small open bell is used to listen to low
frequency heart sounds. The bell picks up sound.
The tubing carries the sound to the ears.
Earpieces keep out external noises and keep sound
loss to a minimum.
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HEARING RANGE AND ULTRASOUNDS
The human hearing range is between 20Hz and
20000Hz. Frequencies above this are called
ULTRASOUNDS and cannot be heard by humans, though
animals like bats and dogs can hear them.
Ultrasounds are used in medicine to produce scans
of the inside of the body (INSIDE WOMB) and high
intensity ultrasounds are used to break up kidney
stones.
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HOW ULTRASOUND SCANNERS WORK.
Ultrasonic waves are produced by a device called
a transducer. This is pressed against the skin of
patient (jelly) and a narrow beam of ultrasounds
scan the body. Some of these are reflected back
whenever they pass from one type of tissue to
another. A computer analyses the information.
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SOUND LEVEL AND NOISE POLLUTION
Sound level is measured in decibels (dB). Some
important sound levels to remember
are threshold of hearing 0dB normal
conversation at 1m 60dB danger level 80dB
threshold of pain 140dB Your hearing can be
damaged by over exposure to loud noises. Ear
protectors are used to absorb the sound energy.
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BENDING LIGHT
LEARNING INTENTION
To show the change of direction of light as it
passes from air to glass, then glass to air.
APPARATUS
Power supply, ray box, single slit, rectangular
block.
INSTRUCTIONS
Normal
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RESULTS
Normal
CONCLUSION
The beam of light moves towards the NORMAL when
it passes from air to glass and away from the
normal when it passes from glass to air.
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Refraction of light in a converging lens.
LEARNING INTENTION
To investigate refraction of light in 2
converging lenses of different thicknesses.
APPARATUS
Power supply, ray box, triple slit 2 convex
lenses (thin thick).
INSTRUCTIONS

(a) Thin convex
(b) Thick convex
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RESULTS
(a) Thin convex
(b) Thick convex
CONCLUSION
The thick convex lense refracts the light more.
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Refraction of light in a diverging lens.
LEARNING INTENTION
To investigate refraction of light of a diverging
lens.
APPARATUS
Power supply, ray box, triple slit, concave lens.
INSTRUCTIONS

Concave lense
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RESULTS
CONCLUSION
The concave lens causes the light to spread out.
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NORMAL SIGHT
Lens
Retina
In normal sight the image is focused accurately
onto the retina when looking at near or far
objects.
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SHORT SIGHT
Lens
Retina
Concave lens for correction
In short sight the image is focused in front of
the retina. Distance vision is worse than near
vision
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LONG SIGHT
Lens
Retina
Convex lens for correction
In long sight the image is focused behind the
retina. Near vision is worse than distance
vision.
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FOCAL LENGTH
The focal length of a lens is illustrated below.
Focal length
Watch the demonstration on how to measure the
focal length of a converging lens. Now you do the
same.
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POWER OF A LENS
The power of a lens is related to its focal
length as shown - power 1/focal
length focal length 1/power Power is
measured in dioptres(D) and the focal length must
be in metres. A convex lens has a positive power
and a concave lens has a negative power.
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LASER

• A laser is a concentrated high- energy beam of
  light. A carbon dioxide laser is used to treat
  tumours. An argon laser is used to repair
  damage to the retina of the eye. An argon laser
  is also used to remove birthmarks.

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ELECTROMAGNETIC SPECTRUM
The electromagnetic spectrumVisible light is
just one type of electromagnetic radiation. There
are various types of electromagnetic radiation
with longer wavelengths of light than red light
and with shorter wavelengths than violet light.
All the different types of electromagnetic waves
travel at the same speed through space.  
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X-RAYS
X-rays pass through soft body tissue but are
absorbed by dense bones in the body. X-rays
darken an unexposed photographic film.
X-rays are used to detect breaks in bones -
the break showing up as a dark line on a
photographic film while the bone appears white.
CAT scanner uses x-ray images from a number of
angles to build up a 3D image of the inside
of the body.  
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ULTRAVIOLET

• Ultraviolet radiation is used to treat skin
  conditions such as acne. UV radiation is
  also used to sterilise equipment because it
  can kill harmful bacteria. Too much
  exposure to uv radiation may produce skin
  cancer.

Ultraviolet radiation is also used in Sun
beds Security pens
Fluorescent lights (coatings inside the
light absorb the ultraviolet light and re-emit it
as visible light).
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INFRARED

• Infrared radiation is another term for heat.
  Infrared radiation is used to treat strained
  muscles and tissue. Infrared radiation is
  also used to diagnose tumours. This works
  because a tumour emits more infrared
  radiation than healthy tissue does. This
  radiation can be detected on a thermogram - a
  photograph taken using infrared radiation.

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RADIATION
Radiation can be defined as energy given off by
the nucleus of an atom in the form of particles
or rays.
Radiation is in every part of our lives. It
occurs naturally in the earth and can reach us
through cosmic rays from outer space. Radiation
may also occur naturally in the water we drink or
the soils in our backyard. It even exists in
food, building materials, and in our own human
bodies.
Radiation is used for scientific purposes,
medical reasons, and to power some submarines. We
can also come into contact with radiation through
sources such as X-rays, nuclear power plants, and
smoke detectors.
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THE ATOM
All nuclear radiation comes from inside the atom.
An atom consists of protons () and neutrons (no
charge) surrounded by electrons (-)
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ALPHA RADIATION
Alpha radiationAlpha radiation consists of alpha
particles. An alpha particle is identical to the
nucleus of a helium atom, which comprises two
protons and two neutrons.  
Alpha radiation can be stopped by a sheet of
paper.
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BETA RADIATION
Beta radiationBeta radiation consists of high
energy electrons emitted from the nucleus. These
electrons have not come from the electron shells
or energy levels around the nucleus. Instead,
they form when a neutron splits into a proton and
an electron. The electron then shoots out of the
nucleus at high speed.
Beta radiation can be stopped by a thin sheet of
aluminium.
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GAMMA RADIATION
Gamma radiationGamma waves have a very high
frequency. Gamma radiation cannot be seen or
felt. It mostly passes through skin and soft
tissue, but some of it is absorbed by cells.

• Gamma radiation is used to
• Sterilise surgical instruments.
• Kill harmful bacteria in food.
• Kill cancer cells (note that lower doses of gamma
  radiation could cause cells to become
  cancerous).

Gamma radiation can be stopped by dense materials
like lead.
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IONISATION
Nuclear radiation can cause electrons to break
free from the atom. When this happens the atom
has become positively charged (a positive ion).
Alpha radiation causes much greater ionisation
than beta or gamma.
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Photographic fogging
When light falls on photographic film the
chemical on the surface changes and the film
blackens (fogs). Alpha, beta and gamma
radiations have a similar effect on photographic
film and can therefore be used to detect it (film
badges for people who work in the nuclear
industry).
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RADIOACTIVE DECAY HALF LIFE
The activity of a radioactive source is a measure
of how much radiation it is giving out. The unit
of activity is the becquerel (Bq).
If a source has an activity of 1Bq then 1 atom
disintegrates each second and gives out a
particle of radiation.
The half life of a source is the time taken for
the source to half its original value.
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MEASURING HALF-LIFE
First of all the background count rate is
measured using a GM tube connected to a counter.
Detecting radiation with a GM Tube
The count rate from the source is measured at
regular fixed intervals over a period of time.
The background count rate is subtracted from each
measurement and the actual count rate from the
source is measured.
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A graph of the count rate of the source against
time is plotted.
From the graph, the time taken for the count rate
to fall by half is measured.
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RADIATION DOSE

• The radiation dose received by body tissue
  depends on the type of radiation absorbed by the
  tissue eg whether the radiation is alpha, beta,
  gamma or some other type of radiation such as
  X-rays. The radiation dose received also depends
  on the energy of the radiation.

A way of expressing the radiation dose received
from different sources is in terms of a quantity
called 'equivalent dose'. Equivalent dose is
measured in sieverts (Sv). A dose of one sievert
from an alpha radiation source, for example, is
equivalent to a dose of one sievert from a beta
radiation source or any other source of radiation.