Aeroplane: An aeroplane usually consists of the following three parts: (i) Wings, (ii) The engine and the propeller; and (iii) The tail. Working: In
order to operate an aeroplane, the propeller is made to revolve at a
very high speed with the help of a powerful petrol engine. The direction
of the blades is so adjusted as to push the air in a backward
direction, thereby producing a relative velocity between the ’plane and
air—thus pushing the aeroplane in a forward direction. The push should
be large enough to overcome the drag and should supply power for
climbing.
Air conditioning: is the process of controlling the
humidity, temperature, purity and circulation of air in a certain
factory, a public building, hotels or a private house. The major aim of
air-conditioning is to regulate the temperature, thereby producing a
“cooling effect” on the whole. Exhaust machines are devised at a
particular place for driving out waste and dirty gases, thereby
completely purifying the air.
Binoculars: is an instrument used for seeing distant objects; the rays of light are twice reflected by means of right-angled prisms.
Carburettor: It is an apparatus for getting liquid fuel mixed with air as it is taken into an automobile or other like engines.
CD-Rom: It is a computer peripheral device that
employs compact disk technology to store large amounts of digitized data
for later retrieval.
Cellular Phone: This phone allows you to make a telephone while on the move. It can be installed in vehicles or can be carried along.
Cinematography: The principle of persistence of
vision is utilised in cinematography. A cinematograph is an apparatus
for projecting the pictures of moving objects on the screen. The
instantaneous photographs of the successive positions of the moving body
are photographed on a continuous film with the help of a special camera
called the movie camera, with an automatic shutter at the rate of
nearly 16 per second. The film duly developed is projected
intermittently with a similar shutter as above so that it opens when the
film is stationary and closes when it jerks off.
Computer: A complicated electronic machine which can
perform incredibly complex calculations at incomprehensible speeds. It
was invented by Charles Babbage. It can do whatever we know how to order
it to perform. A computer consists of a Central Processing Unit
(C.P.U.) and a number of peripheral units. A computer does not do
anything which a human being cannot do. Only that it does is much faster
and accurately.
Dewar Flask: is a double-walled glass flask, the
inner surface of the outer vessel and the outer surface of the inner
vessel of which have been silvered. The vacuum is created in the space
between the two walls. This principle successfully prevents any
interchange of temperature of the contents, because: (1) glass is a bad
conductor (2) convection is not possible because there is vacuum between
the walls and (3) a little radiation that takes place from the inner
vessel is reflected by the inner surface of the outer wall.
Daniel Cell: In this a rod of zinc is placed in
dilute sulphuric acid contained in a cylindrical porous pot. The porous
pot and its contents are placed in a large cylindrical copper vessel
which also functions as positive pole of the cell. The space between the
porous pot and the copper vessel is occupied by a solution of copper
sulphate. The hydrogen produced by the action of the zinc on sulphuric
acid travels towards the copper electrode. On delivering its electricity
to the copper, it reacts with the copper sulphate turning copper out of
the solution and forming sulphuric acid. The particles of copper
liberated from the solution adhere to the outer copper vessel and thus
the hydrogen is rendered harmless so far as polarisation is concerned.
Diesel Engine: It is a particular type of internal
combustion engine, known as compression ignition engine. The air inside
the cylinder is usually compressed to over 500 lbs. per sq. in. and the
temperature is attained up to 800°F. At this stage the oil is injected
into the hot compressed air, which gets ignited immediately, thereby
producing a continuous gas stream, which pushes the piston upward. And
thereafter the engine gets into operation.
Dynamo: The origin of the electricity in a dynamo is
the transformation of mechanical energy into electrical energy. It
depends on the principle of electro-magnetic induction whereby a current
is produced on traversing a magnetic field.
Electric Bell: In an electric bell, there is one
horse-shoe electromagnet, which plays an important role. A soft iron
armature which is connected to a hammer H, is placed in front of the
pole pieces of the electromagnet.
One end of the coil of the electromagnet is connected to the terminal T2
while the other end is connected indirectly to the terminal T1 (i.e.,
through the soft iron armature which rests on the spring contact as
shown in the diagram).
On connecting the terminals T1 and T2 through battery, the electromagnet
attracts the soft iron piece, and the hammer H in turn strikes the gong
G, which produces a sound. Simultaneously, the contact between the
spring and the screw breaks which demagnetises the electromagnet and the
soft iron piece falls back to make up the circuit once again. The
process is repeated again and again, which produces a continuous sound.
Electric Lamp: The electric lamp is based on the
principle that when an electric current is passed through a very fine
metallic filament inside an evacuated glass bulb, it is heated so as to
render the wire white hot or incandescent. The wire being very thin
offers great resistance to the passage of the current so that
considerable heat is developed and the temperature rises to make it
luminous and thus emit light. The resistance generally increases as the
temperature rises and soon an equilibrium is reached and there is no
further rise of temperature, the amount of heat radiated by the filament
being equal to that generated in it by the electric current. In order
that the metallic filament shall not oxidise or rust, oxygen is removed
from the bulb by pumping out air or generally some inert gas such as
nitrogen or some other gas is made to fill the bulb.
Electric Motor: An electric motor is a device which
converts electrical energy into mechanical energy. A D.C. motor
generally consists of several segments of a coil of a wire of a large
number of turns wound over a soft iron cylinder called the armature. It
is mounted on an axle about which it revolves and is placed between the
poles of an electromagnet called the field magnets. There are the
commutator, brushes and the leads. It is based on the principle that a
conductor carrying current experiences a force when placed in a magnetic
field.
Electro Cardio-gram (E.C.G.): It is actually a
graphic picture of the heart-beat which the physician can make use of in
the diagnosis. When the heart beats, its muscles contract and this
causes a change in the electrical potential of the system. This change
in potential is recorded on a paper by an electrical instrument known as
electrocardiograph. The electrodes are connected to the two wrists and
the left leg of the patient, and the machine acts like a galvanometer,
the needle of which rests on a rotating drum covered with a paper, and
thus the movements of the needle are recorded.
Electromagnet: whenever an electric current passed
through a coil of wire, a large number of turns, wound round a soft iron
core, the iron core gets magnetised and it becomes a powerful magnet,
and is known as an electromagnet. This magnetism is temporary and lasts
so long as the current passes through the coil. Looking at the end of
the soft iron bar if the current in the coil is clockwise in direction
that end of the bar is South Pole; if the current is counter-clockwise,
that end is a North Pole.
Electron Microscope: It is just analogous to optical
microscope in a way that beams of electrons are focused by magnetic
lenses in a similar way to the focusing of light beams in the ordinary
optical microscope. Germans were the pioneer to invent the electron
microscope, during the year 1930. Direct magnification up to 10,000
times is possible. Still higher magnification is possible with the
Proton Microscope.
FAX: Short for facsimile, it is a device that
transmits pictures, drawings, text to a similar device at the receiving
end, using telephone lines.
Fibre Optics: It is a branch of physics based on the
transmission of light through transparent fibres of glass or plastic.
These optical fibres can carry light over distances ranging from a few
inches or centimetres to more more than 100 miles (160 kilometres). Such
fibres work individually or in bundles. Some individual fibres measure
less than 0.004 millimetre in diameter.
Optical fibres have a highly transparent core of glass or plastic
surrounded by a covering called a cladding. Light impulses from a laser,
a light bulb, or some other source enter one end of the optical fibre.
As light travels through the core, it is typically kept inside it by the
cladding. The cladding is designed to bend or reflect-inward-light rays
that strike its inside surface. At the other end of the fibre, a
detector, such as a photosensitive device or the human eye, receives the
light.
Uses of Optical Fibres: Optical fibres have a
number of uses. Various industries use optical fibres to measure
temperature, pressure, acceleration, and voltage. In fibre-optic
communication systems, lasers transmit coded messages by flashing on and
off at high speeds. The messages travel through optical fibres to
interpreting devices that decode the messages, converting them back into
the form of the original signal. Fibre-optic communication systems have
a number of features that make them superior to systems that use
traditional copper cables. For example, they have a much larger
information-carrying capacity and are not subject to electrical
interference. In addition, signals sent over long-distance fibre-optic
cables need less amplification than do signals sent over copper cables
of equal length.
Optical fibres are well-suited for medical use. They can be made in
extremely thin, flexible strands for insertion into the blood vessels,
lungs, and other hollow parts of the body. Optical fibres are used in a
number of techniques that enable physicians to look and work inside the
body through tiny incisions.
Fire Extinguisher: works by spraying continuous
streams of carbon dioxide gas, which does not support combustion, and so
acts as a fire extinguishing agent. Fire extinguisher is a medium size
metallic cylinder fitted with a head-knob and a handle. At the time of
emergency, the knob is struck against the floor, and carbon dioxide gas
begins to evolve. Inside this cylinder a bottle of dilute solution of
sulphuric acid is embedded in sodium carbonate powder. When the bottle
is broken, sulphuric acid reacts with sodium carbonate to produce large
quantities of the gas.
Fusion Torch: is an instrument to be evolved by the
U.S. Atomic Energy Commission. It will use the power of the Hydrogen
bomb to vaporise solid waste like junk-cars and bearcans, into their
basic elements. The idea is based on the assumption that within a few
years scientists will be able to harness the energy of the Hydrogen
bomb—Controlled thermo-nuclear fusion—for use in electrical power
plants.
Geiger Counter: A G.M. counter or Geiger-Muller counter is a device used for detecting and/or counting nuclear radiation and particles.
Heart Lung Machine: A machine which operates the
function of the heart and lung at the time when the heart or lung is
under operation. It directs the circulation of blood into body.
Incandescent lamp: If a body of sufficiently high
melting point say platinum wire is raised to a high temperature, some of
the radiations coming out fall within the range termed “light”. The
range comprises of radiation of short wave lengths and high frequencies.
When such a body is heated it emits different colours at different
temperatures, and ultimately, it gives dazzling white light at 1500°C
and above. So the incandescent lamp consists of a metal of a high
melting point (generally tungsten) enclosed in an evacuated glass globe
and heated by an electric current. The filament is either in the form of
an open spiral of straight wire or in the form of a ring of coiled
wire. This lamp consumes about 1.4 watt per candle.
Internal Combustion Engine: is an engine in which
energy supplied by a burning fuel is directly transformed into
mechanical energy by the controlled combustion of the fuel in an
enclosed cylinder behind a piston. It is usually applied to the petrol-
burning or Diesel oil-burning engine.
Jet Engine: The essential components of the jet
engine is the Gas turbine. It drives the rotary air compressor, which
supplies compressed air to the combustion chamber, where a fuel like
kerosene oil or gasoline enters and burns. The hot exploded gases are
then expelled to the rear in a high velocity jet exhaust. It is the
reaction of the plane on this jet of ejected gases that drives it
forward.
Jet Propulsion: It is now being commonly employed
for propulsion of aircraft and the underlying principle is Newton’s
third law of motion, that is, “to every action there is an equal and
opposite reaction”. Here a gas turbine drives the rotary air compressor
which supplies compressed air to the combustion chamber, where the
fuel-like gasoline enters and burns. The hot exploded gases are expelled
to the rear in a high velocity jet exhaust. It is the reaction of the
‘plane on this jet of fastly ejected gases that drives it forward. It
has made possible supersonic speeds.
Difference between Rocket and Jet Engine: The
essential difference between the propulsion of a jet engine and a rocket
is that the gas turbines used in a jet engine require air to supply
oxygen for the burning of the fuel. Rockets contain both fuel and an
oxidizer to make them burn. Liquid oxygen is often used. So a jet engine
would work only in the lower strata of the atmosphere where sufficient
oxygen can be supplied by the air-compressors. The high velocity jet
from a rocket is available for thrust in the upper atmosphere and even
beyond the limits of our atmosphere. For rocket flights of course, the
wings and rudders would be absolutely useless since there would be no
air to exert force on them.
LASER: or Light Amplification by Stimulated Emission
of Radiation, LASER is a device that harnesses light to produce an
intense beam of radiation of a very pure, single colour. The power of
the beam can be low (as in a food store laser scanner which reads prices
on packages) or high (as in lasers used to cut metals). The first laser
was built in 1960.
Lightning Conductor: It consists of a metal rod, the
upper part of which is made up of copper with a number of conical
points, the lower portion being an iron strip which extends deep into
the earth’s moist layers. A lightning conductor protects the building
from the effect of lightning in two ways: (i) The pointed conductors are
charged by induction oppositely thus setting up an opposite wind which
brings about a slow and silent discharge of the cloud. (ii) If however
the lightning does strike, the discharge may be carried to the earth
through the metal strip without doing any damage to the building. In
ships also, lightning conductors are fixed to the masts and carried down
through the ship’s keel-sheathing.
Loud Speaker: It is a device for converting
electrical energy into sound energy. There are various types of loud
speakers but the commonest and most efficient type used now-a-days is
the moving coil type. It is based on the principle that when a varying
current is passed through a conductor in a magnetic field, the conductor
is acted on by a variable force and if the current is oscillatory, the
conductor is set into vibrations.
Mariner’s Compass: is an apparatus which is used to
guide the sailors. The needle always points north-south. It consists of a
magnetised bar with a card bearing the directions viz., north, south,
east etc. The card is correctly mounted above and firmly attached to the
magnetised bar. When the magnet moves in relation to the ship’s course,
the card automatically moves with it.
Motor-Car: A motor-car usually consists of the
following working parts: (i) Internal combustion engine (ii) Gear Box
(iii) Battery (iv) Carburettor (v) Dynamo (vi) Radiator.
Working: In order to operate a motor-car, the
petrol from a container is ignited with the help of the battery. The
vapours produced thereof are allowed to mix with air in the carburettor
section, and thereafter the mixture is allowed to enter the cylinder of
the internal combustion engine. The gases on expansion push the piston
upwards thereby moving the crank-shaft, which in turn moves the main
axle of the car. The motion of axle is controlled by the gear box.
Periscope: It is a device for viewing objects which
are above the eye-level of the observer, or are placed so that direct
vision is obstructed. It is usually used by the crew of a submarine to
survey the ships etc., on the surface of the sea while the submarine is
under water. It also enables sailors to observe objects on the other
side of an obstacle without exposing themselves. It consists of a long
tube, at each end of which is a right-angled prism, so situated that, by
total internal reflection at the longest faces, light is turned through
an angle of 90° by each prism. The light from a viewed object thus
enters the observer’s eye in a direction parallel to, but below, the
original direction of the object.
Phytotron: is a big machine costing two million
dollars and capable of producing any type of climate to order. It has
been installed in Duke University, Durham, North Carolina to facilitate
studies of environmental biology—particularly growing of plants under
varying climatic conditions. The machine can duplicate any set of
climatic conditions from the tropical to the Arctic in the brick and
glass building in which it is housed. It has six specially equipped
green houses and 40 controlled plant chambers. It is a useful device for
the study of environmental biology.
Radar: precisely means: Radio, Angle, Detection And
Range. It is one of the interesting developments of wireless waves the
principle of which has been utilised in the radio location technique or
popularly known as RADAR. It is an electrical device used for the
detection and location of the aircraft with the help of radio frequency
waves.
Working: Wireless waves having very short
wavelengths are set free in the shape of concentrated beam to flood or
cover the required area of the sky. An aircraft entering that particular
area is supposed to intercept the spreading waves, and an echo is
reflected back to the transmitting station. In addition to detection of
the aircraft, its distance from a particular place can also be
calculated by recording the time taken by the wireless waves in
travelling back. A discrimination between the aircraft of an enemy and a
friendly nation can be made by understanding the nature of Echo.
Refrigerator: It is an apparatus or chamber for
producing and maintaining a low temperature. The principle employed in
the working of a refrigerator is that heat is absorbed by a liquid as it
evaporates, thus producing a cooling effect. The substance commonly
employed is liquid ammonia sulphur dioxide.
Rocket: The underlying principle of the flight of a
rocket is Newton’s Third Law of Motion viz., To every action there is an
equal and opposite reaction. It is a self-propelled vehicle which
depends upon the force provided by a fuel carried along with it. As the
fuel burns, products of combustion are forced out at terrific speed at
the rear of the vehicle and ejection imparts motion to it in the forward
direction. It has its own oxygen supply for burning the fuel and
therefore, there is no dependence on air for combustion or propulsion.
Rocket Bomb: If a rocket engine is used as a missile
to carry an explosive charge it is termed as a Rocket Bomb. The
principle of a rocket engine is the same as that of a jet engine but
unlike the jet engine it carries its supply of oxygen with it to burn
the fuel and is thus independent of the oxygen of the air. The hot gases
formed in the combustion of the fuel are led through a nozzle. If a
quantity of gas of mass m leaves the nozzle in time t with a velocity v,
the force exerted on the mass of gas and hence the force also on the
rocket = mv/t. Such a rocket bomb can be hurled from a place outside our
atmosphere.
Safety Lamp, Davy’s: It is based on the principle of
rapid conduction of heat by a metal. In the miner’s safety lamp, the
flame of the lamp is surrounded by glass and above this is a space
surrounded by five copper gauzes. Inflammable gases which may be present
in the mine can pass through and burn inside the lamp. The copper gauze
conducts away the heat so rapidly and effectively that the ignition
point of the gas outside the gauze is never reached and thus the
possibility of an explosion is avoided.
Seismograph: It is an instrument used for the
registration of earth tremors, and consists of principle of a heavy
pendulum system, the supporting framework following the ground movements
and the bob remaining at rest on account of its large inertia thereby
setting up a relative movement between the two parts of the seismograph.
This movement is recorded with the help of electromagnetic transducers,
galvanometers and electronic amplifiers. In order to record the
displacements completely, usually three seismographs are made to set at
one particular station.
Sound Barrier: Before the advent of aircraft with
supersonic speeds, it was apprehended that when the speeds of the
aircraft and sound were equal, the compressional waves produced by the
flight of the aircraft will be unable to get away and will give rise to a
sound barrier which will offer a considerable resistance to the motion
of the aircraft and huge structural stresses and strains will be called
into play attended by great noise likely to react unfavourably on the
crew. But no such effects have been observed now that the speed of the
jet-propelled aircraft and rockets far exceeds that of sound.
Spring Balance: A Spring Balance is used for
measuring weights. The principle involved is that the stretching in the
case of a Spring is proportional to the load suspended and if a load of 1
kilogram produces a stretching of 1 cm, a load of two kilograms will
stretch it by 2 cm and so on. The spring is held at the upper end and
load is suspended by a hook attached to the lower end with a pointer
attached to the upper end of the spring which moves over a scale.
Steam Engine: is a machine utilizing steam power
through a device by virtue of which heat is converted into mechanical
energy. The steam engine has two main parts: (i) boiler, and (ii) proper
engine. It consists essentially of a cylinder in which a piston is
moved backwards and forwards by the expansion of steam under pressure.
Stereoscope: It is an optical device that makes
photographs seem to have three dimensions. An ordinary camera sees
things only in a flat plane and never in the round. But if two cameras
set several inches apart photograph the same object simultaneously, and
if these two photographs are then mounted side by side and viewed
through a combination of lenses and prisms in such a manner that the two
units enter the two eyes without strain, the resulting mental picture
(image) appear to have three dimensions. Everything is seen in the
round, the way our two eyes normally view things. These are employed in
aerial survey and in astronomical telescopes.
Submarine: may be regarded as a ship having a
variable and controllable specific gravity. It is equipped with large
ballast tanks (in the low, the middle and the stern of the ship) into
which water can be admitted through valves so that the vessel can be
made to sink when desired. On the water being expelled again by pumps
worked by compressed air, the ship rises to the surface. Inside the
water it is the electric motors which drive it forward and there are
horizontal rudders (or hydroplanes) which are fitted on both sides of
the vessel so that by tilting them the vessel is gradually submerged,
the same rudders help to maintain it at a desired depth of submergence.
Tape Recorder: It is an instrument which converts
sound waves into electrical impulses which are recorded as a wavy groove
on the tape. When it is required to produce the voice, the electrical
impulses are again converted into sound waves.
Telephone: It is a device to produce sound to enable
two persons to talk to each other from distance. The circuit, which is
closed when the line is connected, consists of a transmitter and a
receiver connected by an electrical conductor. The transmitter which is
usually a carbon microphone causes variable electrical impulses to flow
through the circuit. In the telephone-receiver, these impulses flow
through a pair of coils of wire wound upon soft iron pole-pieces which
are attached to the poles of a magnet. An iron diaphragm near these
coils experiences variable pulls and vibrates so as to produce sounds
corresponding to those made into the microphone.
Telephotography: is a process by which the
transmission of moving objects is made by radio from one place to
another. A succession of still pictures is transmitted at the rate of
twenty-five per second which gives an illusion of continuous movement.
The television camera changes the light pattern of the transmitted scene
into a series of electrical signals which modulate a very high
frequency radio carrier wave. The received signals are changed into
light variations and reassembled on the screen of a cathode-ray tube at
the receiver.
Teleprinter: It is an instrument which prints
automatically messages sent from one place to another. It consists of a
telegraph transmitter with a type-writter key-board by which characters
of a message are transmitted electrically in combination of 5 units,
being recorded similarly by the receiving instrument. The receiving
instrument then translates the matter mechanically into printed
characters.
Telescope: A simple refracting astronomical
telescope is an optical arrangement for seeing very distant objects. Two
convex lenses are mounted at the ends of two tubes so that by sliding
one tube within the other, the distance between the lenses can be
changed and the images thereby can be focused correctly. The lens at the
larger end of the telescope is of considerable focal length and is
called the object glass and a smaller lens of short focal length is
called the eye-piece. Parallel rays proceeding from a distant object
form its real image at the principal focus of the object glass. The
position of the eye-piece is adjusted so that a magnified virtual image
of it is seen. Since the real image is inverted, this virtual image is
also upside down—a fact of little importance in astronomical work. For
viewing terrestrial objects, the real image formed by the object glass
is re-inverted by another convex lens before it is magnified by the
eye-piece.
Television: It is the transmission of images of
moving objects by radio waves. The scene to be transmitted or its image
on a photo-mosaic inside an iconoscope camera is scanned with the help
of a fine beam of light traversing horizontally and vertically. The
reflected pulses in the former case are picked up by photoelectric cells
which convert light energy into varying electric currents, or in the
latter case, the photo-mosaic with the help of suitable electrical
circuits generates varying currents. These currents are amplified with
the help of valve amplifiers and are then made to modulate the carrier
waves from a transmitter. At the receiving station, the electrical
vibrations are reconverted into light waves which are collected on the
fluorescent screen of a cathode ray oscilloscope at the same rate with
which they are generated at the sending station. With the help of the
property of persistence of vision possessed by the eye, we can see on
the screen an exact photograph of the transmitted scene.
Thermometer, Clinical: A clinical thermometer is
used to note the temperature of a human body and has graduations from
65°F to 100°F. It consists of a thin glass bulb connected with a thick
walled capillary tube known as the stem. There is a constriction in the
bore near the bulb. When the thermometer is placed below the tongue (or
in the arm-pit) of a person, mercury in the bulb gets heated and
expands. The force of expansion pushes the mercury past the
constriction, which thus rises into the stem. When thermometer is
removed, the temperature falls and mercury contracts. But the level
remains intact as the thread is now broken at the constriction. The
temperature can thus be conveniently read. The mercury can be again
brought into the bulb by giving it a slight jerk.
Thermos Flask (Vacuum Flask): It is used to keep hot
liquids hot and cold liquids cold. The principles involved in its
construction are: (i) It is made of glass which is a bad conductor of
heat; (ii) As there is vacuum between the walls, convection is not
possible; (iii) The outer face of the inner vessel is silvered, so there
is very little radiation as polished surfaces are bad radiators. The
inner surface of the outer vessel is polished which serves as a good
reflector of any small radiation from the inner surface.
Tokamak T-3: is a machine designed by Russians to
harness fusion reaction for peaceful purposes. A fusion reaction takes
place under extreme pressure and temperatures such as exist in the core
of the sun. In this machine such conditions are created by generating a
hot gas or plasma. The Russians are already at work on an improved
version of the machine which should achieve self-supporting generation
of fusion-energy.
Transformer: It is an apparatus by which the voltage
of an alternating current is made higher (step-up Transformer) or lower
(step-down Transformer) or its frequency. Transformer is made up of two
coils, one of a small number of turns of thick wire and the other of a
great number of turns of thin wire. A current going through the first of
these causes an induction current of higher voltage in the second. If
the main current goes through the second one, induction current of a
lower voltage is generated in the first coil.
Transistor: It is an active component of an electric
circuit which may be used as an amplifier or detector. It consists of a
small block of a semi-conducting material to which at least three
electrical contacts are made, two of them being closely spaced
rectifying contacts generally and one ohmic or loose (non-rectifying)
contact. Transistors are now being used in radio receivers, in
electronic computers, in electronic control equipments, in place of
vacuum tubes where the required voltages are not too high. They are much
smaller than their vacuum tube counterparts, consume less power and
have no filaments to burn out.
Ultrasonoscope: It is a compact, diagnostic
instrument designed to measure and use ultrasonic sound (with a
frequency higher than 20,000 cycles per second, beyond human hearing).
It emits brief bursts of ultrasound which are reflected back by bone,
fluid or tissue in the body and give an “echo-gram”. The instrument can
be helpful in detecting deep-seated brain tumours, defective heart
valves and abnormal growths.
Videophone: The world’s first commercial videophone
service was started for limited experimental use in Pittsburgh,
Pennsylvania. It is as much of an advance on the ordinary telephone as
the addition of sound and colour was to the movies. The visual dimension
also increases the functional utility of this communication apparatus,
but the trouble so far has been in designing and making videophones
which will be cheap enough to be installed and used by thousands of
people.
