How does ballast-less track provide safe travel?

Ballast is a prime component of the track that acts as a vibrant medium to transmit from the rail surface the weight of the train down to the formation, the wells set on prepared terrain. It ensures a cushioned and smooth run for the train and precludes the longitudinal displacement of the rail called creep. In ballast-less track, as the name suggests the ballast is replaced by a bed of concrete.
          The rails rest on rubber pads placed over concrete sleepers, which are fixed on the concrete bed. The ballast-less track helps to eliminate the evils of dust and noise pollution and proves suitable for underground railway also. So it is also safe for travel.

Like ordinary paints do metallic paints also fade?

Metallic paints do fade. It depends on the quality and the type of the aluminium paste used. Usually in most of the metallic paints, the commonly used pigment is aluminium pigment in the form of paste. Two types of aluminium pigments are available in the market. One is leafing, and the other is the non-leafing aluminium pigment will not get dispersed (or dispersed partially) with the resin while mixing, whereas the non-leafing will get completely dispersed with the resin during mixing.
            So, if the metallic paint contains the leafing aluminium pigment it will get faded over a period of time, whereas if it contains a non-leafing aluminium pigment it will not fade for a longer period.Example: The street lampposts on the roads and highways which are coated with metallic paints appear dull after a short period of coating, whereas cars coated with metallic paints shine even after a long time.

Why do runners run in anti-clockwise direction?

As the heart is on the left side, for humans and animals, running anticlockwise makes the centrifugal force of the body to act from left to right.Whereas it is from right to left for clockwise running.
        Superior venacava (the principal vein carrying blood to the heart) takes blood to the heart aided by heart suction.This vein carries blood from left to right.
        Centrifugal force due to anticlockwise running helps this suction.If we run clockwise, the centrifugal force impedes suction. That is why, in olden days, health officers ensured that all carnival merri-go-rounds were run only in the anticlockwise direction.
        Racing tracks, animal shows in circuses, bullock-drawn pelton wheels, all mostly have only left turns. Stairways in temple towers have only left turns for going up. Clockwise running tires people, especially, children, easily.

What is the principle of photo-chromatic glasses?

Photo-chromatic glasses become dark (activated) when kept under bright light especially when the wavelength of the incident light is in the range of 320-400 nm(nanometres).Darkened glasses get bleached when kept in the dark or under light of longer wavelenghts, 550-650 nm.Both these processes occur simultaneously during daylight and the glass's transparency depends on the predominant reaction taking place in it.
                     These processes are based on the possibility to split and recombine silver and chloride ions in silver chloride using light of different wavelenghts.It is the same principle which is used in photography also. However, in photography, the chlorine and silver ions are separated and not allowed to recombine. In photochromatic glasses, the chloride ions cannot diffuse far away from the silver ions as they are held tightly in a glass matrix. Hence when the 'activating energy' is withdrawn, they recombine to form silver halide. The speed(or rate) of the reaction depends on the doping level of the halide with a catalyst(cooper).
                   Choice of the halides, crystals' size (usually 40-100 Angstroms), concentration, glass type and sensitising dopants are all factors that decide the final behaviour of photochromatic glasses used in light-control, displays, memory applications and optical data processing.

In what way are spatial sound, wide sound and surround sound different from stereo sound?

Let's look at at the way a home music system work.The standard format for home music systems (or FM radio or even television) is the two-channel sound,which is otherwise known as Stereo sound.It is nothing but the two-channel recording,in which sound is played on speakers on either side of the receiver/listener.In the broader sense,stereo effect just recreates the experience of being present at the event.
          Surround sound refers to multi-channel systems.To be more specific, multi-channel systems designed by 'Dolby Laboratories'.It also refers to home theatre multi-channel audio systems, in which sound originates from multiple directions.
         Spatial sound is very much concerned with the concept of localisation.Humans and animals as well hear sound in three dimensions and the very fact is that the perception of spatial aspects of sound is essential to our survival.That is, Spatial waves or sound are well recognised by person since his ear-body-brain combination correctly decodes waves. Assume you are listening to a recorded sound where there is a lack of sensational ambiance, a separation of the instruments and a perception of context of the performance.
        A keen observation reveals that something is missing here. Yes. The missing stuff happens to the Spatial effect or detail. To quote an example, both Virtual Reality (VR) and High Definition Television(HDTV) require spatial sound reproduction apart from what ordinary stereo can offer.But there remains no proof that no commercially available system can successfully convey the natural spatial hearing experience or effect.
       Wide sound is more or less similar to Surround sound. To be more precise, it's a type of sound that is intermediate between stereo and surround effect. The frequency range lies between that of stereo and surround ones.

How does a compact fluorescent lamp consume less electricity than conventional fluorescent lamps and bulbs?

Fluorescent lamps are based on the phenomenon of gas discharge between two electrodes at the ends of the glass tube.Generally these tubes contain a little mercury in the low-vapour phase.When sufficiently large voltage is appiled between the electrodes,some atoms of the vapour get ionised.
The process of ionisation starts with stray electrons and ions that are generally present in the vapour.The electron-ion pair so formed gets accelerated towards electrodes of opposite electrical polarity,gaining kinetic energy.When they collide neutral mercury atoms,some of them are ionised and some are electronically exicted.Excited atoms release their energy in the form of electromagnetic radiation,part of which is in the visible and in the infrared regions of the spectrum.But it is rich in the visible ultraviolet region.
         A fluorescent light source has the inner surface of its glass tube painted with a material called phosphor.Zinc sulphide is the commonest example of a phosphor.But phosphor used in particle are complex mixtures of the sulphides and phosphates of barium,strontium and rare earth elements.These phosphors have the property of absorbing ultraviolet component of the radiation and re-emitting a major fractrion of the corresponding energy in the form of visible light.This enhances the lamp's efficiency of converting electrical energy into visible light.
         The ordinary fluorescent lamp works with a supply voltage of about 220 volt.Since the start of the discharge process demands a little higher voltage,it also employs a starter and ballast(a choke coil) that together produce the desired voltage.On the other hand, the compact tube works at about 400 volt(constant), which is produced by a transformer arrangement embedded in its base.
         Higher efficiency means low consumption of electrical energy.A filament lamp has the lowest efficiency, because is is based on the fact that a material body heated to a high temerature emits radition of all wavelenghts.This radition is richer in the infrared part of the spectrum and since there is no mechanism of converting this into visible light, it has poor efficiency.The three types of lamps may have a typical efficiency ratio of 8:6:3.

Why does a mushroom shaped cloud form after a nuclear bomb explosion?

When a nuclear weapon explodes,there is a rapid release of a large amount of energy within a small volume.This results in significant increase in temperature and pressure.The temperature may be a few tens of million degrees and pressure a few million times the atmospheric pressure.At this temperature,all the material present in the weapon will be converted into hot compressed gases.
Within a fraction of a millionth of a second of the explosion, the weapon's residues emit large amounts of energy mainly in the form of X-rays.The surrounding atmosphere absorbs this energy.This results in the formation of a blazzing, highly luminous, spherical mass of air and gaseous weapon residue called the fireball.
             Within an extremely short time after the explosion,the fireball from a high yield nuclear weapon will be about 130 meters across increasing to about 1700 meters in ten seconds.The fireball expands rapidly engulfing the surround air.
             The ball of hot air is less dense than the surrounding air.It rises swiftly like a hot air balloon.This rising column pulls up debris of the weapon,dust and moisture along with it forming cloud.As it moves up,it cools gradually and reaches about 10km where the atmosphere is extremely stable.The ball of air mass moving up does not have enough energy to penetrate this stable layer.It flattens out.As the relatively warmer layers at the bottom push up,the top layer spread laterally and equally in all directions and the cooler denser layer descend at he edges,giving a distint mushroom shape.