A note on the Hydrogen spectrum

The emission spectrum of atomic hydrogen is given by this amazing spectral series diagram:

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Let’s take a closer look at only the visible portion of the spectrum i.e the Balmer series.

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If a hydrogen lamp and a diffraction grating just happen to be with you, you can take a look at the hydrogen lamp through the diffraction grating, these lines are what you would see:

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Source

These are known emission lines and they occur when the hydrogen atoms in the lamp return to a state of lower energy from an excited energy state.

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           Representation of emission and absorption using the Bohr’s model

Here’s another scenario that could also happen:

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You have a bright source of light with a continuous spectrum and in between the source and the screen, you introduce a gas (here, sodium)

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Source: Harvard Natural sciences

The gas absorbs light at particular frequencies and therefore we get dark lines in the spectrum.

This is known as absorption line. The following diagram summarizes what was told thus-far in a single image:

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The absorption and emission spectrum for hydrogen look like so :

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Stars and Hydrogen

One of the comments from the previous post was to show raw spectrum data of what was being presented to get a better visual aid.

Therefore,the following spectrum is a spectrum of a star taken from the Sloan Digital Sky Survey (SDSS)

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                                 Plot of wavelength vs median-flux

Here’s the spectrum with all the absorption lines labelled:

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Source: SDSS

You can clearly see the Balmer series of hydrogen beautifully encoded in this spectrum that was taken from a star that is light-years away.

And astronomers learn to grow and love these lines and identify them immediately in any spectrum, for they give you crucial information about the nature of the star, its age, its composition and so much more.

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Source: xkcd

Have a great day!

*If you squint your eyes a bit more you can find other absorption lines from other atoms embedded in the spectrum as well.

fuckyeahphysica:

I have always been fascinated by Pokemon.

Tiding through the waves of time, now that I think about it : Pokemon did teach me a lot about physics, especially electricity. 

What is Electricity ?

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Electricity stems from a potential difference between two areas,
which allows for electromotive force to ensue in mobile electrons.

Bio-electricity

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In biological cells, a voltage imbalance or a cell potential difference exists between the inside and outside of a a cell.

The cell achieves this by removing 3 sodium ions for every 2 potassium ions allows into the system. The removing process consumes energy ( ATP ).

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                               The sodium ions leaving the cell 

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                            The Potassium ions entering the cell

Source Video

Pikachu and Bioelectrogenesis

Where does pikachu gets it’s electrical powers ? 

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Its by a process known as bioelectrogenesis.

Bioelectrogenesis is the generation of electricity by living organisms

How it works is rather blunt. Remember I told you that the cells are maintained in a potential difference.

There are passageways /electrolytes that are present that allows a flow of ions through them.

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                                            Ion Passageways

When required,
the brain of the pikachu sends a signal through the nervous system to these
electrolytes, opening ions channels and reversing charge polarity,
causing an abrupt difference in electric potential.

The final effect is the generation of electric current, capable of going up to 100,000 Volts during its thunderbolt move.

Result : Opponent stupefied.

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Water is better conductor than air

Most of animals that bioelectrogenic in nature are aquatic creatures ( electric eels, rays, cattlefish, etc ) . This is because water is a much better electrical conductor than air, therefore electrical signals signals can be transmitted through water.

This betters the chance for the organism to protect itself against predators. Pikachu is not aquatic because probably the writes didn’t want it be so – Poetic License ;P

More:

Some other pokemons that were also bioelectrogenic  were:
Eelektrik and the Eelektross

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The voice of Pikachu – must watch

Electrogenic Humans

The one that ash has is a male pikachu. There is a female to the species as well. ( Look at the tail )

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That’s pokemon physics for you folks.

Hope you enjoyed reading this post as much i did drafting it. Oh boy! There is physics just in about everything !

The Chandler Wobble

Earth precesses around its axis every ~26000 years.

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But in addition to this precession, there is an extra wobble that was observed by Kustner and later followed up by Seth Carlo Chandler, Jr called the Chandler Wobble that occurs at a much smaller time scale.


In 1888, Kustner found that the latitude of Berlin had changed slightly
during his observations of the night sky.

Therefore in 1891,Chandler. decided to conduct a 14 month study examining this change. The following is a plot of the spiral path taken by the earth’s axis over that 14 month  period.

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The following plot shows the motion from 1909 – 2001.

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                                                   Source

Although many theories indicate that this is due to the fact that earth is not a perfect spherical rigid body, it is still not entirely clear on the mechanism that drives earth into this small wobbly motion.

If you took a closer look at the plots you would find that this wobble is of the order of a couple of meters which most certainly does not seem like a lot.

But if you are an astronomer if you do not account for this correction, you might just end up pointing your telescope at the wrong object

Have a great day!

Pillars of creation, Lick Observatory, 2018 [RAW]

Having recently attended a workshop at the Lick Observatory and the opportunity to observe at the telescopes there, this is the raw data of the pillars of creation that we were able to capture using the Nickel Telescope whilst there. 

Exposure time: 300 seconds

Location : M16 (Eagle Nebula)

This image needs to reduced even further to correct for the anomalies in
color that one can observe on the image and that’s something we are
currently working on.  We hope to share the entire data with you in a month’s time after post-processing.

Have a good one!

Pantograph and Trains

Pantograph is a very interesting device that you may find on the roof of electric trains, trams or electric buses.

And the primary purpose that it serves is to collect power from the overhead power line to run the motors of the train without losing contact at higher speeds.

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The train takes the current
from the over head line and the current flows to the tracks
which are earthed at regular intervals via the axle brush on the train.

This completes the circuit.

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                                               Source

The overhead lines are kept in tension and dropper wires are placed at multiple locations to ensure that the contact wire does not bend under its own weight.

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And since any two objects that rub against each other, constant frictional contact would wear them out, the Pantograph and the contact wires have a sliding contact.

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This results in less wear for both the Pantograph and the contact wires resulting in lesser maintenance.

Graphite conducts electricity extremely well while also working great as a lubricant due to it’s self-lubricating properties and therefore most contact strips on the Pantographs are made up of Graphite.

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It’s a very simple apparatus with an extremely pivotal role and that’s what makes  the Pantograph special. Have a great day!

* Trolley pole

** Third Rail

*** Arcing is a serious problem when we are dealing with any high voltage lines. in bullet trains which operate under higher voltages, the Pantographs are always forced to be in contact with the contact wires through a dynamic lever-spring mechanism. (Source)

There are the Sketches of the four moons of Jupiter (Io, Europa, Ganymede and Callisto), as seen by Galileo
through his telescope.

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                                                 Source

The drawing depicts observations from the time period January 7 to 24, 1610.

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The above is the sequence of photographs taken by JunoCam aboard the Juno
spacecraft, in June 2016, of Jupiter and the motion of the four Galilean
moons, as the spacecraft approached the planet.

* There are 79 known moons of Jupiter.

** Jupiter has 4 rings.

Emojis of the cosmos

Pareidolia  is a psychological phenomenon in which the mind responds to a stimulus, usually an image or a sound, by perceiving a familiar pattern where none exists.

These are merely some images of stars and galaxies taken by the Hubble Space Telescope. But what do you see ?

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

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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.

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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.

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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.

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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

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                                                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

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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!

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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.

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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.

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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.

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                                        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.

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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.

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                                              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.

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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:

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Notice the oval nature of the green dots.

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

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The diffraction pattern that you obtain is the following:

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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:

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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.

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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.