SCIENCE CAPSULES

EBOLA VIRUS     Imagine  a huge ship standing in the ocean near the beach and also a football floating on the ocean waves.  The waves does not care the football.  That is, the waves are not at all disturbed by the ball.  But the waves are deflected and reflected by the ship.  So the ocean waves "sees" the ship because it is bigger than the wave.  But the waves are "blind" to the ball because it is smaller than the waves.        A virus or  a group of molecules are having the size in the order of nanometer(10^-9m).  But the wavelength of visible light is in the range of 10^-6 to 10^-8 m. .  Since light waves are bigger than virus like object, it cannot see them.  Hence the optical microscope fails in this region.      So people turned to use other waves.  They found that the particle electron behaves like  waves.  Its wavelength is smaller than that of light (10^-...

  1 .       Mathematics of the pendulum is complicated. 2 .        Frequency of oscillation of a pendulum depends only on its length. 3 .       Time period or frequency does not depend on mass or material of the bob. 4 .         Pendulum’s energy alternates between potential and kinetic and hence it oscillates . 5 .        Potential energy and kinetic energy have opposite relationship and the total energy is conserved. 6 .         Tension along the string (upwards) and weight of the bob (downwards) are only the two forces acting in the pendulum. 7 .         Mainly gravity is responsible for the pendulum’s swings.  Hence ‘g’ can be measured with a pendulum. 8 .        Pendulum always tries to reach equilibrium (center position).  But overshoots it due to inertia 9 .   ...

  Definition:  "When a particle is subjected to two sine wave motion or two oscillatory motion at right angles, the particle describes lissajous figures".      We know sine wave motion and circular motion is basically same.  Hence we draw two circles A and B perpendicular to each other.  The circle B rotates twice faster than circle A.  That is, frequency of circle B is two times than that of A.        A particle at the intersection of two circles is subjected to two sine wave motion   A and B at 90 degree simultaneously.  The particle will describe figures depending on the frequency and phase of A and B .  In our case, the ratio of frequency is  1:2 and the two waves are in phase.        To draw lissajous figures :  A moving point in both the circles are chosen.   Here we should remember; during the time taken by the circle A to complete one rotation, circle B comple...

      When a body vibrates- for example voice box in the throat- sound waves are produced.  They travel as a pressure wave in the air medium. In atoms, when an electron accelerates, it looses energy in the form of light waves.  They travel as electromagnetic wave without the help of the medium.        Since sound is produced by big objects, their wavelength is also big. (From 17 meter to 17 mm).  Since light is atomic phenomenon, their wavelength is smaller.  (From 400 nanometer to 700 nanometer).      We know , the speed of sound and light is vastly different(330 m/s and 3*10^8 m/s).  Hence we see the lightning first and hear thunder later.      Frequency of sound waves is responsible for the pitch and tone.  Frequency of light waves is responsible for the colour and energy.      Sound can be electronically amplified.  The amplification of light is LASER.  ...

      Simple harmonic motion is the another name for oscillation.  Consider oscillating simple pendulum.  Here the energy alternates between potential and kinetic.  Hence the pendulum oscillates until it is damped by air resistance.  Oscillations give rise to many kind of waves in physics. 1. Oscillating water particles give rise to mechanical water waves 2. Vibrating air molecules is the cause of sound waves. 3. A loop of wire oscillates in a magnetic field and produces electric waves(alternating current). 4. Oscillating charged particles emit electromagnetic waves.   etc;

    Imagine a point rotating on a circular path.  Also imagine a normal line drawn from the point and its foot always touching a diameter.  Again imagine radius connecting the point from the center.  As the point rotates ,  the foot of the normal line  will oscillate on the diameter(simple harmonic motion).  And also as the point rotate, the radius connecting the point will be sweeping the angles.  The sine of those angles will make a wavy graph.      Hence rotation, oscillations, and waves are similar motions and can be related.  Remember rotation of a coil in a generator  produces wavy alternating current.    

      Throw a stone in a calm water surface.  The water particles are set in vibration at the point of disturbance.  This particles cause neighboring particles to oscillate.  These particles disturb their neighboring particles.  Thus the disturbance, vibrations or energy is transfered through the surface of water.  We can see circular waves spreading from the point of disturbance.      The wave is energy conducted through the medium using the vibrations of the particles of the medium.  But the particles themselves are never displaced.      All mechanical waves likes sound waves, string waves,tsunami, earthquake moves in this fashion. When a political idea travels through the minds of the people , we call it a wave.