Shadows are not always black!

Shadows are absolutely
fascinating to play around with.

In this Exploratorium demonstration
you can see that a black shadow is only a subset of shadows that can be
formed on the screen.

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If you have multiple sources of light with different colors, then you can additively combine colors to get shadows of various shades.

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In this case where you have multiple sources of light, only when the object blocks off light from all three colored light sources do you get a black shadow.

Since we do not deal with multiple colored sources of light on a daily basis, go ahead, give this simple experiment a try. It’s totally worth it!

Have a good one!

** Other FYP explorations on Shadows :

Can a single point of light always illuminate an entire room ?

On disappearing shadows of Birds and airplanes

     

Can you crush a soda can with lightning ?

Here you can see the lightning striking the empire state building three times.

As you might know skyscrapers like these have a lightning rod that will carry the lightning bolt’s electrical charge through
the path of least resistance along the cable into the ground, reducing
the risk of fire or heat damage from the strike.

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But you might know from high school or college physics that when you have two current carrying wires parallel to each other, then they experience an attractive force towards each other.

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                                               Source Video                    

Lightning carries 30000 amps

An average bolt of negative lightning carries an electric current of 30,000 amperes (30 kA).

So if you were to pass such high currents through a rod, then surely they must experience a substantial magnetic force towards each other and get crushed right ?

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Absolutely, Physics always works ! Have a look at this metal tube:

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This is what would happen when electric lightning is passed through a metal tube. Using magnetic forces to compress electrical filaments is known as ‘Pinching’.

Can Crusher

One cool application for this would be for forming metal cans into interesting shapes.

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As soon as the spark gap fires the capacitor discharges an enormous amount
of current through the coil (tens of thousands of amperes).  This
discharge creates a magnetic field around the coil. 

As the flux lines
pass through the cross section of the can, current is induced and flows
around the can.

 This induced current creates its own magnetic field
which opposes the magnetic field from the coil.  Between the two magnetic
fields there is now a force pushing inward on the can and outward on the
coil.  Once the force is strong enough the can is crushed.

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And with large enough voltage, one can blow the can in opposite directions too!

From generating X-rays to forming of metal into shapes, Pinches have a lot of interesting applications. The references section of the wikipedia is surely a fun ride; check it out and have a good one!

So, our physics teacher has the strange idea of motivating his students by letting each of us present a physical phenomenal we find interesting to our classmates in a 5-minutes-presentation. And now I need something that is interesting for everyone – even people that usually don’t care for physics -, but has interesting facts for someone who’s interested in it, too (preferably with an easy experiment). You don’t happen to have any ideas, do you?

First of all, your professor is awesome for taking the time to do this. Of the top of my mind, the best one I have is Chladni figures.

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Basically take a flat metal plate, fix it at the center and spray some fine sand particles on it.

Using a violin bow, gently excite any edge of the plate to magically witness these beautiful normal mode patterns ( known as Chladni patterns/figures ) forming on the plate.

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Also notice that by pinching the plate at different points, the pattern obtained changes.

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There is a whole lot of physics that goes behind such a simple phenomenon and I dare say we understand it completely. There are lots of questions on these figures that we have no answer for!

Hope this helps with your presentation. Have a good one!

Gif source video: Steve Mould

fuckyeahphysica:

Colors are nature’s way of expressing beauty. And we often find ourselves in this situation where we want to capture this ecstasy. A camera rose out of this innate longing to capture and invariably store these memories.

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Generally when people are on the lookout for buying new phones/cameras, one of the parameters that is looked into is the MP(Megapixels) of the camera.

2.0 MP means that there are ~2million ‘effective’ pixels on the image that has been captured. *

But,what is a pixel ?

Pixel ( or picture element ) is a small element on the screen that represents a specific color. 

But how do you represent any color – with the primary color system of course!! Add the red, blue and green in varying proportions and voila! you can span the entire color spectrum. **

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Therefore,every pixel is constituted of 3 ‘compartments’ – Red, Green and Blue to produce the necessary color distribution of an image.

The subtlety of a screen

Wait!! Hold on are you saying that there are millions of red, green and blue lights on my screen ?

Don’t believe me ? Take a took at these images of a smart phone screen under 30x and 60x magnification.

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                  One RGB block is called a pixel. Video Source : Microworld

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Now this ‘array type of arrangement’ is not necessarily the case with all manufacturers.

In fact, most manufacturers have their own unique type of representation ( see below )and the type varies with the type of application as well.

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                                Photo credit: Peter Halasz. (User:Pengo)

If you have a tough time realizing how a set of RGB lights flashing on a screen is able to project a crisp image, then try this out:

Turn an excel sheet into an image

On the fundamental level, yes! it is merely a set of lights.

But once you start stacking a lot of these pixels next to one other in a grid ( 2 million of them for a 2.0 MP camera! ), you can start to see how a beautiful image emerges out.

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Convert any image to a excel sheet here and explore !

To think that are millions of pixels on the screen rendering the plethora of images that I behold everyday BLOWS my mind out of proportions ;D
Have a great day!


Do more megapixels mean better picture quality ? Sort of but not always!

** What is additive color mixing ? Its not the same as you do with paint!

Small balloons exert higher pressure ???!!!

If you are aware that flow occurs only from a higher pressure to a lower pressure, then the balloon demonstration must have startled you.

This is because according to the demo, the smaller balloon is under high pressure. How is this even possible ?

Have you been this guy ?

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Sucks big time right ? Its so hard to initially inflate the balloon,! But once you get going, its an easier task to handle. Here’s an
intuitive explanation :

Pressure is really the force that molecules
exert on the surface.

When you make that initial blow, you are adding a
significantly large number of molecules into the balloon. (think of it as adding a lot of people in a very small room ) And as a
result, the molecules exert a high pressure.

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But once the balloon
is inflated, the molecules have lot of room to move around, so they do
not do around bombarding the surface that often. Hence the decreasing pressure.

( the rate at which room size increases is more than sufficient enough to accommodate the people in it )/

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                                Variation of pressure v/s radius

This goes by the name – Two balloon experiment. Click here for a more technical explanation.

** DO TRY THIS AT HOME

I encourage you to try this at home to truly appreciate the demonstration. If you have only balloon, then inflate it fully, and then release it by holding the balloon by its neck;

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Feel the pressure of the air that is coming out. ( If will increase as the balloon size decreases )

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Have a great day!

The Smoke Angels.

Wingtip vortices shown in flare smoke left behind a C-17 Globemaster III.

How does an aircraft fly?
Think of it like this, due to the design of the wing, larger number of
air molecules are hitting the bottom portion of the aircraft than the
top.

As a result, a upward force acts on the wing, hence the wing lifts!

This works fine till we get to the wing tips.

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In
the wingtip, the air from a higher pressure wants to move to the region
of lower pressure. And as a result, this forms vortices ( fancy name
for the swirling motion of air ) known as Wingtip Vortex. ( because its
formed in the wing tips!!! )

And it is due to the ramification of this, that we obtain those gorgeous smoke angels. Pretty cool huh ?

Have a great day !

A computational paradigm

I was posed a question by an anonymous follower whether the following animation could be easily simulated on a computer. 

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In today’s world, lots of research are being aided by using numerical methods. But it is quintessential to note that computational methods alone are not enough to dictate behavior of the natural world. It is with the amalgamation of experiments that it’s beauty exemplifies.

The butterfly effect

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One of the many reasons its hard to predict behavior ( say the weather for instance ) is primarily because of the errors that are induced whilst recording it. 

And these errors evolve with time. Let’s take the trivial example of a double pendulum.

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Notice how a slight variation in initial angle with horizontal axis of the blue pendulum causes a huge aberration in the result.

Flow past a cylinder

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When experiments are carried out under controlled conditions, it is possible to observe and simulate phenomenon.

But like it was pointed out before,the simulation per se is proportional to the accuracy of the instruments used to make the measurements themselves.

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So, yeah it is possible to simulate a system such as the one asked, considering crucial boundary conditions are known to us with considerable precision.

And as the complexity of the problem evolves, the computation time and power required also increases exponentially.

Thanks for asking, Have a great day!

fuckyeahphysica:

Chain Reaction.

Everyone knows that a line of standing dominos creates a fun chain reaction when you knock the first one over; but did you know you can use increasingly larger dominos and get the same result? 

The setup.

Professor Stephen Morris knocks over a 1-meter tall domino that weighs over 100 pounds by starting with a 5mm high by 1mm thick domino.He uses a size ratio of 1.5, meaning each domino is one and a half times larger than the last one. This is the generally accepted maximum ratio that dominos can have to successfully knock each other over.

Hans Van Leeuwen of Leiden University in the Netherlands, published a paper online showing that, theoretically, you could have a size ratio of up to two. But that’s in an ideal (and probably unrealistic) situation.

Fun fact.

There are 13 dominoes in this sequence. If Professor Morris used 29 dominoes in total, with the next one always being 1.5x larger, the last domino would be the height of the Empire State Building.

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Source: Physics Buzz.

That’s how a revolving fan works

This gif has been circulating throughout the internet for many years, and I am not denying it It’s pretty darn cool!

Although it gets the mechanism spot on, but it misses out on one of the most amazing part of the mechanism : the oscillation itself.

How does it oscillate?

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                       Source

The oscillation is simple but ingenious. So, you see that pink rod? Yeah that is attached to v – type wedge, like so:

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89 is a pin. And that pin is constrained to oscillate between the two wedges. The angle of oscillation is primarily between 40-100 degrees.

It is this wedge that controls the oscillation.

Why does it oscillate?

The oscillation is due to an eccentric round cam present under the yellow gear. ( seen in animation too )

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An eccentric cam

The rotation of this cam induces a torque which causes the linkage ( the pink rod ) to sweep across the plane.

Important Note

I understand that this explanation is not exactly the finest. But this mechanism has not been explored anywhere else on the Internet .This is what i could reckon of the Patent.

If you have a better explanation/sources/anything at all then please reblog it with this post, that way everyone wins. It is our humble request.

Have a good day!