FSc ICS Notes Physics XI Short Questions & Definitions Chapter 8 Waves 1st Year Physics Notes Online Taleem Ilm Hub
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Mechanical waves: The waves which require a medium for their
movement.
Electromagnetic waves: Transverse waves in spaces having an electric component and a magnetic component.
Matter waves: These waves carry energy and pilot the particle and move along with it.
Wave: A disturbance in the medium.
Water waves: The waves produced in the water.
Ripples: Tiny waves on the surface of water; any slight curling wave.
Ripple tank: An apparatus which consists of a rectangular tray containing water, fitted with glass bottom.
Shock waves: Waves of compression and rarefaction that originate in the neighbourhood of sharp points or roughness on obstacles exposed to the flow of a compressible fluid at high speeds.
Ultrasonic frequency: A sound frequency above the range normally audible by humans, i.e. greater than about 20 KHz.
Ultrasonics: Study and application of mechanical vibrations with frequencies beyond limits of hearing of the human ear, i.e. with frequencies about 20 KHz and upwards.
Ultrasonic waves: Sound waves having frequency greater than 20 KHz.
Radar: (Radio Direction And Ranging) A system for locating distant objects by means of reflected radio waves, usually of microwave frequency.
Radar speed trap: An instrument used to detect the speed of moving object on the basis of Doppler shift.
Oscillation: A vibration; a periodic variation of an electrical quantity, as current or voltage.
Space: That which has length, breadth, and height, and is unlimited in extension.
Guitar: A six stringed instrument played with the fingers.
Music: The art or science of making pleasing or harmonious combinations of sound tones.
Aeroplane: An aircraft or flying machine, kept aloft by the
reaction of motor-propelled planes upon the air.
Electric field: Region in which an electric force acts on a charge brought into that region.
Magnetic field: The region or space near a magnet where the effects of magnetism such as the deflection of a compass needle can be detected.
String: A small cord; thick thread.
Spring: An elastic object or device usually of metal of spiral shape, that yields under a distorting force and returns to its original form when the force is removed.
Magnifying glass (or Simple microscope): An ordinary convex lens held close to the eye.
Pebble: A small roundish stone, worn smooth, as by water.
Progressive wave: The wave, which transfers energy away from the source.
Traveling waves: Waves produced by a driving force, and they travel away from the source which produces them.
Longitudinal wave: The wave in which the particles of the medium vibrate parallel to the propagation of the wave.
Hump: To make such shape like the back of a camel; bend or curve as the back
Energy: The ability or capacity for doing work.
Momentum: In a moving body, the product of its mass and velocity.
Wave: A disturbance in the medium.
Pulse: Single unrepeated disturbance.
Jerk: To give a sudden quick pull, twist or push to.
Slinky spring: A loose spring which has small initial length but relatively large extended length.
Sag: T sink or hang down by weight, or under pressure; as the rope sags.
Transverse waves: The waves in which particles of the medium are displaced in a direction perpendicular to the direction of propagation of waves.
Longitudinal waves: The waves in which the particles of the medium have displacements along the direction of propagation of waves.
Periodic motion: Any kind of regularly repeated motion, such as the swinging of a pendulum, the orbiting of a satellite, the vibration of a source of sound, or an electromagnetic wave.
Periodic waves: Any kind of regularly repeated waves.
Snap: To produce a sharp sudden sound; to throw or seize with a jerk.
Snapshot: An instantaneous photograph.
Rhythm (rhythmic adv.): The regular recurrence (i.e. coming back at intervals) as in music, stress, speech, or quantity; movement marked by a regular measured recurrence of sound.
Vibrator: A device for producing an alternating current by periodically interrupting or reversing the current obtained from a direct-current source.
Crest: A region of upward displacement in a transverse wave.
Trough: A region of downward displacement in a transverse wave.
Harmonic motion: A regularly repeated sequence that can be expressed as the sum of a set of sine waves. Each component sine wave represents a possible simple harmonic motion.
Amplitude: The maximum distance traveled by a vibrating particle from its mean position.
Wavelength: The distance between two consecutive wave fronts.
Snapshot: An instantaneous photograph.
Profile: Drawing an outline of a curved or sweeping figure.
Sine curve: The curve made by plotting the function of y = sin θ.
Transverse periodic waves: The transverse waves which pass one after the other through any point in the medium periodically.
Longitudinal periodic waves: The longitudinal waves in which the particles of the medium vibrate with simple harmonic motion.
Compression: The region of a longitudinal wave in which the vibrating particles are closer than their equilibrium distance.
Rarefaction: The region of a longitudinal wave in which the vibrating particles are farther apart than their equilibrium distance.
Compressional waves (or longitudinal waves): i) Waves in which the particles of the medium vibrate to and fro along the path which the waves travel through the medium. ii) The waves in which the vibrations are parallel to the direction of travel of the wave.
Sound: The series of disturbances in matter to which the human ear is sensitive. Also similar disturbances in matter above and below the normal range of human hearing.
Inertia: i) It is a property by virtue of which it is necessary to exert a force on a body at rest if it is to be set into motion. ii) The resistance of matter to any acceleration of its state of rest or motion.
Elastic modulus: The ratio of stress on a body to the strain produced.
Elasticity: The property of a material body to regain its original condition, on the removal of the deforming forces.
Bulk modulus: Elasticity of volume, corresponding to volume strain.
Young’s modulus: Linear elasticity, or elasticity of length.
Rigidity modulus: Elasticity of shape.
Density: The ratio of the mass of a substance to its volume.
Boyle’s law: The volume of a given mass of a gas in inversely proportional to the pressure, if the temperature is kept constant.
S.T.P. : (Standard temperature and pressure) The standard temperature is 0 oC (273 K) and the standard pressure is 1 atm or 760 mm of Hg or 760 torr or 101325 Nm-2.
Newton’s formula for the velocity of sound: Velocity of sound is directly proportional to the square root of the elasticity and inversely proportional to the square root of the density of the medium. Mathematically, V = √ E / ρ
Laplace’s correction: In calculations of the velocity of sound, to use coefficient of adiabatic elasticity and not to use isothermal elasticity.
Molar specific heat at constant volume, CV: The amount of heat energy required to raise the temperature of one mole of a gas through 1 K at constant volume.
Molar specific heat at constant pressure, CP: The amount of heat energy required to raise the temperature of one mole of a gas through 1 K at constant pressure.
The ratio ( γ ): It is the ratio of adiabatic elasticity to isothermal elasticity; it is the ratio of Cp to CV . or γ = Cp / CV
Binomial theorem: It mathematical form is, (1 ± x)n = 1 ± nx + n(n – 1) x2 + …… (x < 1)1! 2!
Mono-atomic: Describing a molecule that consists of a single atom. The rarer gases are mono-atomic.
Diatomic: Describing a molecule that consists of two atoms; e.g. H2 , O2 & N2 .
Polyatomic: Describing a molecule that consists of several atoms (three or more) e.g. Benzene C6 H6.
Bat: Any of an order of insect-eating animals, with soft, furry body, and wings formed by skin stretched between the fingers, legs, and tail, which fly by night.
Coefficient of volume expansion (β): The change in unit volume of a substance when its temperature is changed one degree.
Absolute temperature: Temperature measured with respect to absolute zero, i.e. zero of Kelvin scale, a scale which cannot take negative value.
Absolute zero: The least possible temperature for all substances. At this temperature the molecules of any substance possess no heat energy. A figure of –273.15 C is generally accepted as the value of absolute zero.
Supersonic: Pertaining to speed in air with a speed exceeding the speed of sound in air.
Ultrasonic: Sounds of frequency higher than 20,000 hertz which are not audible to human ear.
Infrasonic: Vibrations in matter below 20 cycles per second.
Auditory sensation area: The region of intensity and frequency bounded by the lower and upper curves of frequency verses intensity level for sound waves.
Threshold of hearing: The intensity of the average faintest audible sound; 10-12 watt /m2
Threshold of pain: The upper intensity level for audible sounds.
Supersonic plane: A plane moving in air with a speed exceeding the speed of sound in air. At this speed shock waves are produced.
Sonic barrier (or sound barrier): The sudden sharp increase in aerodynamic drag experienced by aircraft approaching the speed of sound.
Sonic boom :
i) An explosive sound caused by the shock wave
preceding an aircraft traveling at or above the speed of sound.
ii) The noise originating from the backward projected shock
waves set up by an aircraft travelling at greater than the speed of sound. A stationary
source of sound emits a series of concentric wave fronts, the radius of which will increase
with time.
Shock waves:
i) A large amplitude compression waves, as that
produced by an explosion or by supersonic motion of a body in a medium.
ii) When an airplane moves relatively slow, air pressure
disturbances move faster than the airplane and are able to disperse. However,
when an airplane moves faster than the speed of sound, air pressure
disturbances are unable to disperse; instead, they amass in front of the
airplane. A cone shaped shockwave forms, audible to those on the ground as a
sonic boom.
Mach number (Ma): The ratio of the speed of a high-speed aircraft to the speed of sound in air; Ma = v / c. An airplane traveling at less than Mach 1 is traveling at subsonic speeds; at about Mach 1, transonic, or approximately the speed of sound; and greater than Mach 1, supersonic speeds; in excess of 5 it is said to be hypersonic. An aircraft flying at Mach 2, for example, is traveling at twice the speed of sound.
Cone: A solid body, which tapers uniformly to a point from a circular base.
Conical surface: The surface made like the outer surface of a cone.
Boeing Company: The world’s largest manufacturer of commercial airplanes and military aircraft. Boeing controls almost two-thirds of the global market for jet airliners. Its headquarters is in Seattle, Washington.
Boeing 747 (called Jumbo Jet): A cargo transport flight with 490 passengers capacity. Four jet engines propel the plane, which reaches cruising speeds of 885 km/hr.
Concord plane: Concord is the only operating commercial supersonic jet airliners. Its speed is 1400 mile/hr with 128-passenger capacity. Both Air France and British Airways operate it.
Falcon: Fighter-bombers aircraft. They are dual purpose aircraft that can drop bombs and also fight enemy planes. e.g. F-16 fighting Falcon.
F-16 (Fighting Falcon): The F-16 is world’s most successful warplane of recent times, over 4000 Falcons have been build. Its speed is 2124 km/hr at 12190 m altitude with range 3890 km. Pakistan have 40 F-16 of A/B model.
Types of planes:
- Land planes: Aircraft that take off from and land on the ground.
- Seaplanes: Aircraft that take off from and land on water.
- Amphibians: Aircraft that can operate on both land and sea.
- Airplanes: They can leave the ground using the jet thrust of their engines or rotating wings and then switch to wing borne flight.
Superposition: Combining the displacements of two or more wave motions algebraically to produce a resultant wave motion.
Principle of superposition of waves:
i) When two (or more)
waves of the same type pass through the same region, the amplitude of vibration at any
point is the algebraic sum of the individual amplitudes.
ii) When two waves act upon a body simultaneously they pass
each other without disturbing each other, and act upon the
particles of the medium quite independent of each other, and their
resultant displacement is the resultant of all individual waves.
Beats:
i) The condition whereby two sound waves form an
outburst of sound followed by an interval of comparative silence.
ii) The periodic alternations of sound between maximum and
minimum.
Stationary waves (or standing waves): i) Waves apparently standing still resulting from the similar wave trains travelling in opposite directions. ii) Resultant of two wave trains of the same wavelength, frequency, and amplitude travelling in opposite directions through the same medium.
Interference: The phenomenon in which the two waves support each other at some points and cancel at others.
Phase coherence: Producing of two waves of same wavelength and time period at the same instant.
Constructive interference:
i) Whenever path difference is an
integral multiple of wavelength displacements, the two waves are added up. This effect is called constructive interference.
ii) The interference of two waves, so that they reinforce one another.
Destructive interference:
i) At points where the
displacements of two waves cancel each other’s effect, the path difference is an odd integral
multiple of half the wavelength. This effect is called destructive
interference.
ii) When two waves overlap each other in opposite phases.
Audio generator: A device to generate electric charges (electrons) to move to and fro repeatedly (A.C. signals) with frequency range of 20 Hz to 20,000 Hz.
Amplifier: A device for reproducing an electrical input at an increased intensity.
Power amplifier: An amplifier producing an appreciable current flow into a relatively low impedance (i.e. the ratio of voltage to current) or a large increase in output power.
Microphone: A device for converting sound energy into electrical energy.
Cathode ray oscilloscope (CRO) : A device used to display input signal into waveform.
Tuning fork: A metal two-prong fork which produces a sound of a definite pitch.
Sonometer: A device consisting of two or more wires or strings stretched over a sounding board, used for testing the frequency of strings and for showing how they vibrate.
Sound waves: Longitudinal wave motion through a material medium produced in matter having frequency range from 20 to 20,000 hertz.
Law of length: The frequency of transverse vibration of a stretched string is inversely proportional to its vibrating length under constant stretching force.
Law of tension: The frequency of transverse vibration of a stretched string is directly proportional to the square root of its tension for given length.
Mathematically; ν ∝ √ T , l
& m are constants.
Law of mass: The frequency of transverse vibration of a
stretched string is inversely proportional to the square root of its mass per unit length
for as given length and constant tension. Mathematically;
ν ∝ √ l / m ,
l & T are constants
Plasticene: A soft plastic material used, especially by children for modeling.
Organ (or organ pipe): A musical instrument played by means of one or more keyboards. It produces sound by means of a vibrating air column enclosed in one or more pipes.
Sitar: Indian instrument, with seven metal strings, a gourd body, and long neck with moveable frets.
Violin: A four stringed musical instrument played with a bow.
Piano: The largest musical stringed instrument. It is enclosed in a case and played from a keyboard.
Guitar: A six stringed instrument played with the fingers.
Reflection: The turning back of a wave from the boundary of a medium.
Stationary waves (or Standing waves):
i) The resultant of
two wave trains of the same wavelength, frequency, and amplitude travelling in opposite directions through the same medium.
ii) Waves apparently standing still resulting from two
similar wave trains travelling in opposite directions.
Node: A point of no disturbance of a stationary wave.
Antinode: A point which oscillate with the maximum amplitude in stationary waves.
Harmonic series: A series having a sequence of numbers, each of which is obtained from the preceding number of the sequence by adding the same number; such as, f, 2f, 3f, etc.
Peg: A small usually cylindrical pointed or tapered piece (as of wood) used to pin down or fasten things or to fit into or close holes.
Organ (or organ pipe): A musical instrument played by means of one or more keyboards. It produces sound by means of a vibrating air column enclosed in one or more pipes.
Flute: A musical wind instrument furnished with finger holes and keys.
Odd: Not exactly divisible by two.
Even: Divisible by two without a remainder.
Stationary longitudinal wave: Stationary waves in which the particles of the medium vibrate parallel to the propagation of the wave.
Fundamental frequency (or Fundamental): The lowest frequency produced by a vibrating object.
Harmonics (or Overtones): The fundamental and the tones whose frequencies are whole number multiples of the fundamental.
Echo: The repetition of sound caused by the reflection of sound waves.
Echolocation: Such location where the echo is heard.
Dolphin: Any of various agile sea mammals, akin to the whales.
Doppler’s effect: The change in the pitch of sound caused by the relative motion of either the source of sound or the listener.
Locomotive: Pertaining to motion or travel from one place to another; an engine or motor for drawing railway cars.
Relative velocity: The vector difference of the two velocities.
Doppler shift: Apparent change in frequency due to relative motion of source and observer.
Artery (pl: Arteries): One of the tubes, which carry blood from the heart.
Vein: One of the tube-like vessels, which carry the blood to or toward the heart.
Electromagnetic waves: Transverse waves in spaces having an electric component and a magnetic component.
Radar: (Radio Direction And Ranging) A system for locating distant objects by means of reflected radio waves, usually of microwave frequency.
Sonar: (SOund NAvigational Ranging) A technique for locating objects underwater by transmitting a pulse of ultrasonic sound and detecting the reflecting pulse.
Satellite: A smaller body that revolves around a larger
body.
Echo: The repetition of a sound or of sounds already heard, caused by the throwing back of sound waves.
Acoustics: Study of the production, properties and propagation of sound waves.
Acoustical: Pertaining to acoustics.
Submarine: Something that functions or operates underwater; such as, a warship designed for under sea operation.
Astronomy: The scientific study of the heavenly bodies, their motions, relative positions, and nature.
Astronomer: One who is skilled in astronomy or who makes observations of heavenly bodies and their phenomena.
Astronaut: Somebody from a non-communist country who travels beyond the Earth.
Cosmonaut: Somebody from a communist country who travels beyond the Earth.
Star: Any celestial body visible as a point of light.
Nova: A faint variable star that can undergo a considerable explosion during which the luminosity increases by up to 105 times.
Supernova: Stars that suffer an explosion becoming some 108 times brighter than the Sun during the process.
Pulsars: Stars that emit radio frequency electromagnetic radiation in brief pulses at extremely regular intervals.
Nebula: A luminous, cloud-like formation seen among the stars. It may represent the initial form of a star cluster that may condense out of it or the final form of a supernova.
Crab Nebula: the name of a star of supernova type.
Black hole: An astronomical body with so high a gravitational field that it causes gravitational self-closer, i.e. a region is formed from which neither particles nor photons can escape, although they can be captured permanently from the outside.
Planet: Any one of the larger celestial bodies of the solar system, revolving round the sun in a nearly circular orbit and shining by reflected light; distinguished from the stars.
Galaxy (or Milky way): The star system to which the Sun and the Solar System belong.
Cosmos: The observed universe regarded as an orderly collection of galaxies, stars, planets, comets, etc.
Spectrum: i) The set colors obtained on the screen by dispersion. ii) Array of colors arranged according to their wave length.
Blue shift: The shift of received wavelength from a star into the shorter region.
Red shift: The shift in the wavelength of light from a star towards longer wavelength region.
Microwave: An electromagnetic wave with a wavelength in the range 1 mm to 100 mm, i.e. with a frequency in the range 300 to 3GHz.
Transmitter: A device used in a telecommunication system to generate and propagate an electrical signal.
Explosion: A sudden and violent outburst from a solid to a gaseous state with a loud report.
Tremor: Quick vibration or shaking.
Prong: Sharp pointed instrument or branch; such as one leg of a tuning fork.
Absorption spectrum: A spectrum having dark lines because of the absorption of some wavelengths.
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