Monthly Archives: November 2017


Fraunhofer Diffraction Means You Can’t See Properly

It’s depressing as you get older and your vision seems to get worse with every passing year.  But in reality the human vision is pretty poor anyway.  You might be able to see a passing ship on the horizon but you won’t be able to read the name on the side at any distance.  Our eyes have pretty useless resolution so images get blurred the further the distance you are.  Of course we can use binoculars to magnify an image but why can’t we see this stuff with the naked eye?

The reason is basically down to the size of our pupils also known as their apertures.  Our eyes need to be open wide enough to let through enough light to make sure that the sensors in the eyes start working.  However the more open the aperture is the more the light entering the pupil will blur.  The reason is that  all the light arriving into our eyes comes from a variety of directions, again the wider open the more directions the light will come from.

 

Most of the light waves come in parallel and form a bright clear central spot.  But the width of this ’clear spot’ is blurred at the edges by light waves arriving in different phases and hence cancelling each other out.  The result is that the edges have a series of light and dark alternating bands but looks very much blurred.    The width of the clear spot is actually what regulates the finest level of detail that our eyes are able to pick up.

Fraunhofer diffraction describes the blurred images that will be observed when the light rays arrive on a lens or aperture like the eye in parallel routes.  It is also known as Far-field diffraction and is easiest seen when we pass a light source from a long way away (perhaps the Sun) through a lens.  It doesn’t matter if the lens is in our eyes or a telescope the effect is the same.  The diffraction effect will also smear the final image for a camera, eye or telescope.  The limit of clarity is imposed when the light is passed through any sort of optical lens.  To learn more about science subjects like this, make a habit of watching the best science programmes.  I’d particularly recommend some of the superb ones being shown on the BBC recently, you can watch on the Iplayer.

If you’re outside the UK you’ll need to change your IP address to view the Iplayer – try this site for downloading from the BBC – http://www.iplayerabroad.com/2017/04/28/download-bbc-iplayer-videos-abroad/   It’s quite easy to do, routing your web connection through a British server takes minutes and gives you full access to all the wonderful BBC Iplayer programmes.

The Electronic Barriers of the Internet

The internet certainly has the capacity for change.  It has the potential for political change, to overthrow dictators, implement social improvements and a myriad of other benefits.  The problem as always is that many people are being put at a distinct advantage when using the web.  It used to be irrelevant where you lived when online, however that is certainly not the case now.  Many countries increasingly used filters or firewalls on their nations internet access. There are of course the extreme cases like North Korean and China where access is highly regulated and monitored.  Although these countries aren’t ideal examples as there is little pretense to providing much more than a glorified intranet.  The Chinese restrictions grow stronger every year and they also have a growing ability to restrict these workarounds including these VPNs and proxies too.  The Chinese want to control where people get their information and their news from – i.e. not from UK TV channels online but State controlled sources.

But on a lower level social sites like Facebook and Twitter are blocked in many other areas from time to time.

If it wasn’t bad enough now commercial barriers are being instigated in the form of geo-targeting.  This technology is used to deliver or restrict access dependent on where you are located. Companies like Hulu for example only want users based in America to access their content so if you try and watch from outside the USA you’ll get blocked.  Even less commercial organisations are doing like the BBC who restrict access to the wonderful iPlayer to the United Kingdom.

However it’s not just media companies either, any large business with and international presence is likely to do the same.  Usually this is down to profit maximization due to a method called price discrimination.  Basically a company needs to be able to offer it’s goods and services at different prices depending on location in order to make the most money.  The internet blasted away these barriers, but they are slowly being rebuilt.  A simple example is the online games retailer – Steam, which offers computer software but at vastly different prices depending on where you are physically located. However they obviously have to stop people from the expensive areas buying from the cheaper ones.

Of course there are ways around it – this post about a Euro VPN server for example illustrates a method to watch BBC Iplayer from anywhere.  But that method involved a subscription service which may well be un-affordable for a huge sector of the internet’s population.  These restrictions stop open access, allow companies to operate shady price discrimination mechanisms and basically just rip the heart out of the internet for many of us.

In the USA there are even more worrying actions – statutes being proposed like Protect IP act which would make web site owners liable for links and content put on their sites. Good luck on running a forum on free speech if that every gets though !  You’d spend more time at the local court defending yourself than running the site.