fuckyeahphysica:

The Touch Screen

One cozy evening, I gazed a lazy look to the surrounding. From the looking glass of a Lazy individual everything looks dull.

But once my vision tuned in on the Smart Phone, it struck me that I had no idea how this thing works but yet have been using it constantly for years. Time to disparage the boredom !

This is an account of the bewitching touch screen world. All Aboard!

The Resistive Touch Screen

image

If you have used a mobile phone in the distant past that involves you pressing down hard on the screen, then there is a great possibility you have used a Resistive touch screen.

Some examples are the Nokia N800, Nokia N97, HTC Tattoo, Samsung Jet or the Nintendo DS.

image

How does it work?

This is the traditional form of a touch screen and its working is rather blunt. There are two conductive sheets present that are separated by spacers.

When you press your hand against the screen , the top layer gets pressed and
makes contact with the bottom layer. This completes an electrical
circuit.

image

The act of pressing reduces the resistance between the two conductive plates. (because you are reducing the distance between these two conductive plates and resistance is dependent on the length of the medium)

The voltage established as a result of this change in resistance is measured and the coordinates of the point of contact are determined.

The harder you press, the more the change in resistance.

This is one of the frustrating things about this type of touch screen.

Resistive touchscreen require slight pressure
in order to register the touch, and are not always as quick to respond.

image

But they are used in many low-budget mobile phones like the Freedom 251, which is a touch screen phone for $3.75.

The Capacitive Touch Screen

image

                                                Source Video

Now over to the touch screen that we are most accustomed with: the capacitive type.

Capacitive touch screens are constructed from materials like copper or indium tin oxide that store electrical charges in an electrostatic grid of tiny wires, each smaller than a human hair

image

When a finger hits the screen a tiny electrical charge is transferred to
the finger to complete the circuit, creating a voltage drop on that
point of the screen.

Due to the transfer of some amount of charge from the screen to your
body. this change will be noted by the monitor placed below the screen
and the exact location of your touch is noted.

Note:

Plastic does not allow charges to flow through. Ergo, if you try to use it whilst wearing gloves or anything plastic / non-conductive materials, the screen will not respond to your touch!

image

But leather or other conductive materials on the other hand will allow charges to pass through, which is why they work well with any smart phone.

image

Hope you guys enjoyed this post . Have a good day!

* Some of these facts may not apply to Rugged phones like the CAT S61 or its variants.

Screens, Lasers and Symmetry

A couple of weeks ago, we discussed about the famous Photograph-51 and how
that led to the discovery of the Double Helix structure of DNA.

We
mentioned in that post that the best way to visualize that diffraction
pattern is by using a laser and pointing it on a helix from a ballpoint
pen.

image

And in the previous post on pixels, we learned about how the RGB pixels arranged on a screen come together to render those beautiful images on your screen.

image

                                        Source : Microworld

The pixel arrangement on a screen need not be periodic like shown above. In fact ,most manufacturers have their own unique type of representation ( see below )and the type varies with the type of application as well.

image

As an amateur physicist you do not have a microscope but only a green laser as your tool, how would you go about finding which one of these arrangement your smartphone has ?

Visualizing pixel spacing using a LASER

For a fact, you know that:

if you shine a red light on a green or blue object, it will
appear black.

image

                                              Source    

So if you take your green laser pointer and shine it on any of those pixel blocks, you know that you are only going to get green light from the green filter.

image

The other two filters will absorb the green light.

And using that you can find out the type of pixel arrangement your smartphone has.

We will be testing it out with Samsung Galaxy S4 whose  pixel arrangement on the screen looks like so:

image

Notice the oval nature of the green dots.

Let’s shine a green laser on the screen observe the resulting diffraction  pattern:

image

The diffraction pattern that you obtain is the following:

image

Observe that the dots on the image are not circles but ovals instead. This is due to the nature of the pixel arrangement on the Galaxy S4.

If you had a good red laser (which we did not) and tried this same experiment, you would get a pattern like so:

image

You are also welcome to try it on a smartphone of your choice or any electronic display and compare it with the pixel arrangement of that particular device.

image

This paper (from which the above image has been taken) runs through some more examples of the diffraction pattern that one obtains from common electronic components.

Have fun!

Related Interesting videos:

LCD Technology: How it Works

How a TV Works in Slow Motion – The Slow Mo Guys

* As with any diffraction pattern, you can measure the distance between the two dots and calculate the distance between two consequent pixels using the wavelength of the light source as given.

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.

image

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. **

image

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.

image

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

image

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.

image

                                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.

image

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!

One of the striking aspects of our solar system is that the orbital plane of all the planets are similar i.e Its like the following:

image

                                                  Source

And not like so:

image

                                                Source

But if you are puny human sitting on earth, how would one visualize this ? It’s easy!

Step out and look at the trajectory taken by the  sun and planets in the sky:

image
image

                                                    Source

image
image

You will notice that the trajectories taken by the sun and the planets are similar in the night sky.

This gives you a visual validation of the fact that the orbital plane of all the planets and the sun are similar. Just a little something that you may or may not have realized about the cosmos.

Go ahead, give it a shot and have fun!

* The ecliptic plane is the name given to the mean plane in the sky that the Sun follows over the course of a year; 

The exotic moves of the human eye

It is always a humbling experience to compare our progress in technology with what nature has been doing for decades on end.

1-2 –> Iris in camera vs human eye

3-4 –> Iris mechanism in camera vs human eye

5-6 –> Accommodation of the eye

Have a good one!

* Pupil dilation video

* Eye contraction video

* Understanding the functioning of the Eye

* Bio-mimicry and eyes

On the definition of  Angular Momentum

Anonymous asked:

Why
is it mr^2 omega and not some other weird formula that is conserved? Why not mr^3 omega or mr^2 omega^2 ?

This is a great question. And to be honest, there is no intuitive answer as to why it is defined this way or that.

What makes the definition special?

Conservation laws can be understood better through the Lagrangian formulation of classical mechanics.

image

That’s the conservation of momentum for a free particle. It means that this quantity mv remains constant with time (not m2v, not m2v2 ,just mv).

And similarly for a rotating body, one can find that the quantity that remains constant wrt time is the angular momentum.

image

And that’s the best rationale using modern physics that can be provided for why Angular momentum takes the form that it does.

Any other form would just not be conserved. Sure, you can construct a Lagrangian that would give you the form that you need but that would not  represent anything physical !

Hope that answers your question. Thanks for asking !

** If you have not heard about Lagrangian formulation of classical mechanics, the wiki article on Principle of Least action is a really good place to start..

The principle of Least/Stationary action remains central in modern physics and mathematics, being applied in thermodynamics, fluid mechanics, the theory of relativity, quantum mechanics, particle physics, and string theory.

Chocolate bar in Microwave (Part-II)

This diagram of the electromagnetic spectrum finds it place in all physics textbooks:

image

                                             Source

But the problem was I never got a physical sense of what that meant. It remained ‘yet another physics diagram’ for a really long time.

You see, unlike sound which can be neatly visualized using Schlieren imagery

image
image

                                       Source: NPR

or by other unconventional innovative means,

image

I had no idea how to even get started with electromagnetic waves.

Visualizing the microwave wavelength using a chocolate and an oven (although not my original idea) arose out of this need to understand microwaves a little better.  (Check out part-I of this post)*

image

But you can do more with some better but less delicious equipment.

You can get a couple of neon bulbs from an electronics shop and place them in a grid inside the microwave to view the standing wave while the microwave is in action

image

                                                    Source

This tells
you how the heat is distributed at the bottom of the microwave oven.
The lit bulbs are anti-nodes and unlit ones are the nodes .

You can also try (NOT recommended) to do this by placing a light bulb inside a cup of water instead of a neon bulbs.

image
image

                                  Better quality gif  – here              

As you can clearly see the bulb only lights up in the anti-node regions
of the standing wave while the remaining regions are the
nodes.

You can take this a step further if you have an infrared camera .

Mark Rober had this brilliant idea of using the infrared camera inside a microwave in order to ensure that food that is being microwaved is cooked evenly and completely on the inside.
   
     
       
       

image

                                              Source

And ElectroBOOM then took this to the next level by placing a cardboard box inside a microwave oven and looking at the heat map using a infrared camera.

image
image

                                    Source: ElectroBOOM                                            

That last gif my dear friends was the most satisfying physics animation that I had ever seen for a really long time ! It clearly illustrates the 3D standing wave heat map that is produced inside a microwave oven.

Although these aren’t the only ways to visualize the standing microwave pattern inside a microwave oven, but these are the ones that I was able to test them out with equipment that you can probably find at home or at school/university.

You are welcome to suggest more thought experiments, alternate methods or edits to this post, I would highly appreciate it!

Have a good one!

* Previous post: Chocolate bar in Microwave (Part-I)

** Why is wavelength of light important than its frequency ?
   
                                   
                                   

Chocolate bar in Microwave (Part-I)

Here’s a fun little experiment that anyone can conduct at home with a chocolate bar and a microwave oven.

Remove turntable from microwave (the plate that rotates)

Take a chocolate bar on a plate and place it inside microwave.

Heat for for 30-60 seconds on high.

You will notice that the chocolate would have melted in some regions and not in others (see image above). But don’t worry this is supposed to happen.

image

                                                 Source 

A microwave works by setting up a standing wave inside it.

The size of the oven is chosen so that the peaks and troughs of the
reflected microwaves line up with the incoming waves and form a “standing
wave”.

image
image

The above is a 1D analog of a standing wave, but a 2D standing wave looks like so:

image

                                                   Source

And there are nodes and anti-notes in three dimensions throughout the entire oven.

At the anti-nodes is where the wave oscillates the most

And therefore a molecule placed at the anti-nodes will rub against each other more rigorously than the ones at the nodes.

More the rubbing, more the food the gets heated up. 

image

This is why the chocolate in our image is melted in some regions (the anti-nodes) whether remains intact in others (the nodes).

If you take a ruler and measure the distance between two successive anti-nodes and plug it into the frequency-wavelength relationship, one can obtain the speed of light.

image

                                                    Source

image

But the key insight that one can gather from this experiment is the visual feel for how long the wavelength of a microwave actually is!

It’s a lot of fun to do this experiment on your own.

image

So we encourage everyone to give it a
shot. We will take a break here and we will dwell into more microwave physics in part-II.

Have fun exploring !

Aircraft operations in Infrared

Taxing

image

                                                 Source

Take-off

image
image

                                                Source

Landing

image

                                                  Source

Reverse Thrust

image

                                                  Source

Deicing

image

                                                    Source

For more interesting aircraft action in IR check out these videos:

* Aircraft inspections in Infrared

** Takeoff, landing and more – as seen from cockpit using IR camera

*** Landing with and without FLIR (Forward Looking Infrared Radar) 

Fluorescent lamp with and without phosphor coating

When an electric current is passed through the mercury vapor that is present inside the Fluorescent lamp, it excites it and produces short-wave ultraviolet light (LEFT).

But a phosphor coating on the inside of the lamp makes it glow white (RIGHT). The type of phosphor coating dictates the color of lamp

image

                                                Source

For example, in the tube above
a coating of red phosphor is applied the right, followed by a band of green, a
band of blue, then with all three mixed together to produce white light,
and finally on the left an uncoated region showing the mercury
discharge inside.

And that’s how we get Fluorescent lamps of different colors!

* More on the working of Fluorescent lamps