SCIENCE CAPSULES

    Light takes 3+  seconds to travel from the moon.  It takes 8 minutes and 17 seconds to travel from the sun. The nearest star alpha centauri is 4.37 light years away. So light propagation is not instantaneous as we experience every day.  It has finite speed 300000000 met/sec in vacuum.        When light travels in denser medium like water or glass,  it slows down.  In glass, it travels at 2*10 ^8 met/sec speed.  The ratio of speed in vacuum to the speed in glass is 1.5 and it is the refractive index of the glass.      Discovery of speed :  Ole roamer observed Jupiter through telescope.  He was able to see the shadow of its moon 'Io" on the face of Jupiter as a blackspot.  When the Jupiter was close to earth, the spot appeared at one place; when the Jupiter was far away  from the earth, the shadow appeared at another place.  From these observations, he was able to calcula...

water drop lens     Lens is everywhere.  It is found in telescope, microscope, camera, projector, binoculars and spectacles and so on.  The lens rules the world even today.      Eye lens is natural one.  At one moment, we can see ant moving on the floor.  The next moment we can see the stars in the sky.  Eye lens can change shape automatically and there by alter its focus according to the distance of the object.  That is a natural wonder.  We still struggle to duplicate it.      Eye lens loses its transparency and become opaque due to aging.  That is cataract.  In cataract surgery, the natural lens is replaced by artificial one.  Cataract surgery is one of the highest numbers of surgeries done worldwide. How to see without spectacles?       You need not worry, if you miss the specs.  A pinhole in a camera box (light tight box) ac...

      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.  ...

      Children love to play with soap bubbles.  The feel, colours, and motion attracts them.  Let us see how the colours appear in the bubbles.      It is a hollow sphere made up of thin film of water.  Only air is inside the bubble.  We know the sunlight contains the famous seven colours.  The sunlight enter and exit the bubble.  There may be several reflected and refracted rays of sunlight in the water film.       At one point in the bubble, the thickness of the film and our viewing angle may be such that; only red light waves(rays) will be in phase (in order); then they will reinforce themselves and red will appear bright in that point.  All other colour waves will be out of phase (in disorder) and they will destroy themselves at that point.      By the same reasoning we can tell, at another point yellow will only appear; at the next point only orange will be bright.  ...

           How do  we see motion in a movie?  Let us find out      Whenever we see an object, its image falls on the screen (retina) of the eyes.  The image does not vanish immediately.  It stays in the retina for sometime(one tenth of a second. ). This is called persistence of the vision .  It may be a natural fault of the eye.  But it helps us to enjoy movie in theater and TV.        Look at the running fan.  The three blades cannot be seen clearly.  It is because the images  fall in the eyes; stays and overlaps.  Hence we see only fuzzy circle.      In a cinema, 16 pictures are projected on the screen in one second.  They fall in our eyes successively  and rapidly.  They create an illusion of continuous motion.  So we perceive movement in the cinema screen and TV from still pictures due to persistence of vision.   ...

   I have two numbers and I want to find the greatest common divisor (GCD) for them.  Then, I have to find all the factors of two numbers and select "the common big one" from both the set of factors.  It will be a tedious task for very big numbers.        There is a sleek procedure(algorithm) to do this .  This algorithm is devised by euclid in 300 B.C.   Let us find out GCD for 30 and 18 in euclid's way .        Divide the big integer by the small integer and get the remainder.         30 MOD 18 = 12 .    Now divide the divisor 18 by the remainder 12 and get the new remainder.         18 MOD 12 = 6 .    Next again, divide the divisor 12 by the remainder 6 and get the fresh remainder.         12 MOD 6 = 0      6 must be the GCD of 30 and 18  because it is derived from both the integers by repeated divisi...

      White is a mixture of all colours or mixture of primary colours.  White surface reflects away all the light.        Black is the absence of light.  Black surface absorbs all the light.       Red, green and blue are said to be the primary colours.  All other millions of colours can be got by adding them properly.    Leaf looks green because it absorbs all the colours from sunlight except green which is reflected away by it.        When red object is viewed using green light, it will look black, because even that green light is absorbed by the red object and no light is emitted.     If an element (sodium, carbon) is burnt, it will emit certain colours of light(spectrum).  It is like signature of the element.  Element can be identified using that colours.       Only red laser and blue laser have been invented so for. ...

     put a spoon in a glass which is half filled with water.  The spoon looks bent, because light traveling from air to water is bent(refracted).  why should light refract?      When light waves travel in a denser medium like water and glass, its slows down.  like we slow down, when we move into a knee deep water.       If all the light waves travels straight(perpendicular to the line of separation of two media) and enter the denser medium, the wave speed will decrease, but they will go undeviated.      But if the waves enter the line of separation at an angle (obliquely), part of the first wave front will enter the denser medium and" that part " will be slowed down; remaining part will move with original speed in the first medium.  This process causes the wavefront to bend.  similarly all the waves that follow will bend (when they enter) and follow a different path in the denser medium. ...