Category: Physics

By Anupum Pant

We’ve always heard mass is a form of energy, mass is frozen energy or mass can be converted to energy. It might sound like you’ve been lied all your life when I tell you all of these statements are not exactly right. Mass is a much more complex thing than it seems.

This channel I recently stumbled upon does a very good job of explaining what mass is by first telling you that the mass of a hydrogen atom is actually slightly less than the sum of masses of it’s constituents – an electron and a proton. The same thing can be applied to a proton too, which is composed of quarks. And so on.

So mass is basically not just a simple indicator of the amount of matter in something. There’s more to it…

By Anupum Pant

At 6 PM and midnight every day, radio 4 in London broadcasts the first chime of the Big Ben on radio. BBC has a microphone placed very closed to the source of the sound which sends it across through BBC and then to your radio at essentially the speed of light. Now, if you have the radio right next to your ear and the BBC’s microphone is right next to the source of the sound, you nearly eliminate all the places where the sound has to travel through air at about 340 metres per second.

That means, if you are standing on the Westminster bridge, a couple of metres from the source of the chime to listen the Big Ben chime, and on the other ear you have the radio, you’ll hear the chime on radio first. Yes, even before you hear it in real life. Assuming you are using a proper analogue FM radio, where there’s no digital encoding and other lags going on.

By Anupum Pant

When you say you see something, you mean that you sense the photons that are being reflected by the object you “see”. What if the object emits hardly any photons? At least not enough for you to see anything?

The answer is, you see black. Remember that this isn’t the average black sharpie colour you see almost everyday. In that case, you see something. Vanta black, is the blackest substance ever created. It absorbs 99.9% of light. That means when you look at it, you actually are not seeing anything. Rather, your brain is looking at objects around it and concluding that there has to be something in the dark part, so let’s make it look black.

By Anupum Pant

Experimentation gives you so many answers that you couldn’t have known otherwise! Consider a simple experiment like this one. There’s a balance. Both the sides have exactly the same kind of beakers and both the beakers have been filled by exactly the same kind of water, to exactly the same level. The balance is still balanced.

Now, the balance is clamped to the balanced position and the following is done:

One beaker’s base is tethered to a ping-pong ball which is completely inside the water.

The other beaker, on the right has an acryllic ball of the same size, submerged at the same level, but is tethered from the outside, suspended from the above into the water.

The balance is then released. Predict which way the balance will tip. Or will it even tip to any side? Do have an answer ready with your own explanation for it. Even the greatest physicists would get stumped here.

Once you are done.

Here is the [Answer]

By Anupum Pant

To make a simple electric train you just need a very long copper wire, a pencil cell and a few magnets. Making the train itself is as simple as sticking the magnets at both the ends of the cell. The track is the wound copper wire with an internal radius that is just enough to fit the “train”. If you make it into a loop and send in your train, it just keeps running till the cell runs out.

By Anupum Pant

Florescence is a physical phenomena in which light (electromagnetic radiation) is absorbed by a substance with certain properties and is instantly emitted back in a different wavelength. Most times the absorbed light of a certain wavelength is emitted back by the substance with a greater wavelength. This leads to one interesting phenomenon in which the smaller wavelength UV radiation (which is invisible to the human eye) gets converted to a visible light by the substance. Applications of this particular phenomenon are numerous, in the modern world.

The white fluorescent lamps we see lighting up most of the things these days (getting quickly replaced by white LEDs) contain a fluorescent substance which does the same thing. The vapour inside these lamps gets excited and produces a UV light, had the fluorescent phosphor coating not been there in these lamps, you wouldn’t have seen any bright light come out of them.

But the most interesting application that I had not known until today is them being used in optical brighteners or fluorescent whitening agents in detergents that are commercially available to help you make your whites appear more white than they actually are. When you treat your clothes with these brighteners, the clothes now have this substance clinging to it which can absorb the UV in sunlight and emit a blue light. So, the yellow from your whites mixes with this blue and you see your clothes are more white in the sun outside.

If people in the military decide to wear whites washed with detergents like these, they’d be in big trouble. It would make them glow in nightvision goggles.

By Anupum Pant

Reaching temperatures really cold, at the point where Nitrogen is a liquid is relatively simple. Just use the liquid Nitrogen you have stored in a nice insulated container. Like that, you could attain temperatures of about 77K (or about -196 degrees centigrade). Going cooler is also simple, use liquid Helium (or about -269 degrees centigrade). Now you’ll reach 4K.

But what if you need to go colder than that? A few experiments like one that measures the extremely tiny change in dimensions of a metal ball due to the gravitational waves needs temperatures like these. That’s because these extremely tiny  changes due to the gravitation waves have to be larger than the movement of atoms in the metal ball itself. And this happens at very low temperatures (in the range of millikelvins). So how do we reach temperatures like those? Dr. Morello explains.

By Anupum Pant

People with big homes must have had trouble placing their WiFi router in a place so perfect that everyone at home gets good signal. With a small flat and a fairly powerful router, I don’t have that problem. However it’s still fun when it’s physics.

A PhD student, from the Imperial College London in the UK who goes by the name Jason Cole has made a brave attempt to model the intensity of electromagnetic radiation emitted from the router across his flat. For this he first mapped his floorplan, assigned refraction values to the walls, and then used the Helmholtz equation to create a simulation.

For us physics amateurs he was kind enough to make get an android app made. It enables everyone with a decently powerful android phone to map their floorplans and simulate the intensity of WiFi signal across their apartments. The app uses what they call it in science, 2D Finite Difference Time Domain method to solve Maxwell’s equation on a Cartesian grid – if you know what I mean. The app can be downloaded for free at the play store.

If you are more of a physics person and would be interested in having a look as to what goes on behind his simulation, go visit Jason’s page here.

By Anupum Pant

Remember the time we saw how a cloud chamber could be made at home? It was very slightly tougher to make than this one I’m going to show you now. This one is much more easier…

By Anupum Pant

Have you tried balancing a small bouncy ball on top of a basketball and then dropped them together? If you haven’t, you should try it once. The bouncy little ball somehow bounces really high, much higher than it would have gone individually. How does that happen?

The difference is massive. Normally the small ball would bounce back about 70% of the height it was dropped from. But the tree ball stack makes it go 8 times the height it was dropped from. That’s a lot, isn’t it?

And then, did you know the tiny ball goes even higher when you have 2 bigger balls under it when they are dropped? How does it all work. Well, for us engineers the understanding comes very naturally, because we try to locate the source where the tiny ball gets the energy, which clearly isn’t from the gravitational potential – As it bounces 8 times its initial height. Physics girl, a relatively newer science channel which has been making really quality videos lately, explains.

By Anupum Pant

Try this at home. Take two grapes, pierce them with a straw or wooden toothpick on both ends and try to balance the contraption from the middle part on a sharp edge. All of it to reduce friction – you get the idea…

Now bring a strong magnet towards it, you’ll repel the grape. Try doing it with the other pole of the magnet. It still goes away. So are grapes magnetic?

Well, intrinsically the grapes are not magnetized, but when you bring a strong magnet closer, it gets magnetized in the field of this magnet. Stronger  the magnet, more is the magnetization. This, because it contains water, which is diamagnetic.

By that logic, even frogs are magnetic. So are water droplets. In the year 2000 Andrey Geim, yes the same person who was given a Nobel prize for isolating graphene using a scotch tape, won an Ignobel prize for levitating a frog, water droplets and a variety of other objects using very strong electromagnets. – Levitation without meditation.

Here’s the levitating frog…

and here are the magnetic grapes…

By Anupum Pant

The simplest and most mundane things can turn out to be really interesting sometimes, if you look carefully. For instance, look at a glass of water, ordinary water. Turn it upside down and the water falls. Actually it shouldn’t!

Yes, gravity acts on it, but the amount of force atmospheric pressure acts on it is enough to support the column of water even when the glass is upside down. It falls because the water surface isn’t flat. And since the pressure acts differently on different parts of the surface, due to minor deviations on the surface, the surface gets deformed and there is an avalanche of force imbalance. Eventually the water gets pulled down by the gravity. This happens too quickly for you to see.

Now, if you use a piece of paper to keep the surface of water perfectly flat, the pressure acts up evenly on water and gravity isn’t able to pull down the water. Nikola demonstrates…