Columnar basalt on the Elie chain walk

I went along the Elie chain walk in Fife. It's along the base of the cliffs and covered in water in part at high tide. To get over the cliffs, there are a series of about 8 chains to hang on to. You can see one just to the left of centre of the top picture. I found columnar basalt in one of the bays - like Fingal's Cave or the Giants' Causeway, that I haven't seen. Basalt is made from oceanic lava, which has a different chemical composition to crust lava. A thick lava flow like this cools when it hits the air. As it cools, the lava contracts. It pulls almost equally in all directions and all parts are doing this. The result is that the interior of the lava flow is cracked up forming the columns. They are usually hexagonal.

Preparing for Lower Sixth Physics #18: Line Spectra

I used my diffraction grating to take this picture of the low energy bulb in the table lamp on my desk. The lamp is on the right, the spectrum I got appears as coloured lines on the left. Notice that I don't get the full rainbow. The lines are said to be DISCRETE - ie not continuous, not flowing into each other like a rainbow would. The explanation is that photons of light, which are packets of light energy, are released by electrons in the atoms of the mercury vapour inside the bulb. You'll remember from GCSE Chemistry that electrons come in levels around the nucleus - 2 on the first level, 8 on the second level, 8 on the third level etc. Electrons can jump from one level to another. When they jump down levels, they release photons. The bigger the jump, the higher the energy. Photon energy = hf, where h is called Planck's constant and f is the frequency. The higher the energy the higher the frequency. Violet has the highest frequency so that line is for the biggest jump. Red has the lowest frequency and so is for the lowest jump. The lines are discrete because there are only certain discrete energy levels. Each element has its own unique pattern of coloured lines because each has its own arrangement of electron energy levels. This is mercury. See second section down on this link for more details http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/atspect2.html

Preparing for Lower Sixth Physics #17: Diffraction Grating

I have previously posted about the way that laser light spreads out when it goes through the narrow gap between two laser blades. It is also possible to do that by painting glass black and using the razor blade to scratch a narrow line on instead. A diffraction grating is glass painted black that has had an awful lots of narrow lines carved into it. In the picture above, the 2 clear rectangles are bits of black painted glass with so many parallel lines carved into them that it now looks clear. The one on the right has 600 lines carved into 1 mm. Think about it!

Now look at the pattern you get when you shine a laser beam through the grating. The dots are symmetrically placed about the centre but become increasingly dim as you move away from the centre. The formula to describe this will be part of the course.

 

 

 

 

 

Lightning conductor at Whitworth Road Cemetery

I was at a funeral in Swindon and spotted this lightning conductor on the chapel. I was surprised when I first learned that an important job of a lightning conductor is to make a lightning strike less likely. If a negatively charged cloud appears overhead, it will repel the free electrons in the metal of the lightning conductor down into the earth. This will leave the tip of the lightning conductor positive. Charge is very effective when concentrated on a small point because it increases the nearby field strength. This means that the tip is able to rip electrons from air atoms, leaving them as positive ions. These positive ions are then repelled upwards by the positive tip. When the positive ions hit the negative cloud, they reduce its charge making a lightning strike less likely. However it is dangerous to try to replicate this by holding up a metal spike in a thunder storm. Is that because the route to earth through the human body has a much higher resistance? I will have to think about that.

Amazing conglomerate rock at Dunnottar Castle

I spotted that the cliffs were like this on the way in and I wondered if the cliff face has been patched up by humans. It doesn't look like natural rock. But a look at the guidebook confirmed that it is a genuine conglomerate rock. The large round pebbles are held together by a natural salt cement. It must be very effective because that lump of rock has resisted the eroding power of the sea and has a large castle on it. The pebbles in the rock are rounded. That means that they had been transported a large distance before settling. Perhaps these were pebbles on the beach of an ancient sea. It is very different from the brockram conglomerate in the Eden Valley which has angular rocks in it. That rock had only travelled a few miles so was not rounded much by transport.

Preparing for Lower Sixth Physics #16: Parallel lines

Here's a power line on northern Germany photographed on the way to Berlin. The very top wire is the earth wire but lower down there are 6 pairs of wires. Electric current travels in all 12 wires simultaneously. If you put two wires end to end, the calculations are simple: total resistance = resistance 1 + resistance 2.
It is more complicated to work out the total resistance if the wires run side by side. You can't just work out the total resistance. You have to calculate the RECIPROCAL of the total resistance which is written as 1/total resistance.
For two wires in parallel,
RECIPROCAL OF TOTAL RESISTANCE = RECEIPROCAL OF RESISTANCE 1 + RECIPROCAL OF RESISTANCE 2.

Or 1/total resistance = 1/resistance1 + 1/resistance2

Preparing for Lower Sixth Physics #15: The wave equation

I spotted this interesting wave pattern looking down from Dunnottar Castle. There was a strong wind blowing in waves as shown and yet they bent round the corner behind the rock. This is an example of knife-edge diffraction, rather than diffraction through a narrow gap. Only the latter is on the course. However, once the waves bent round the corner, they got closer together as they went on. This is clear on the photograph. The wind blown waves and the diffracted waves must have the same frequency because they are the same waves - caused by the same thing.

The wave equation states:   wave speed = frequency x wavelength.

So if the frequency remains the same but the wavelength decreases, the speed of the waves must have decreased. They have probably slowed down due to friction on the seaweed.

Theory 1 was correct

This picture, taken a day later, shows that Theory 1 in my last blog post was correct. There are no luminous lit up clouds in the far distance. They are all grey. The distant patch of sea is clearly being lit up by sunlight shining back through holes in the distant cloud. So it can only be that the vertical wave surfaces are reflecting the sunlight back in my direction. I had binoculars with me on this occasion and was able to confirm that it was true.

Reflecting on Dunnottar Castle

Dunnottar Castle is in an amazing setting. It is on a tall pillar of rock almost cut off. It;s what a proper castle should be like - ie a bit Game of Thrones - and you can pay to go in. It's worth the trip to Stonehaven to see it. As you can see, I was having trouble photographing it into the Sun. I've been posting before about working out that the colour of the sea is usually a reflection of the sky. So think about the bright sections of sea furthest away on these photographs. They look like they are directly reflecting the Sun because they are in line with the Sun. But there's a problem - they are effectively behind the Sun. Sunlight has to bounce down and up off the sea so that the angle of incidence = angle of reflection. That should light up somewhere in the foreground. Light can't easily go away and then bounce forwards. Here are two possible theories. 1. That the waves were strong that day because of the wind. This presents a vertical reflecting surface that will fire light forwards again. 2. That the Sun is brightly illuminating clouds in the distance and this is what is reflected. I'll have to check theory 1 on a calm day.

The colour of the sea at Stonehaven

This is a view looking out to sea at Stonehaven near Aberdeen on the north east coast of Scotland. Standing there, it was obvious that the nearer water was blue and further out the water looked green. It is less obvious on the photograph, which is disappointing, but you can almost convince yourself if you enlarge it. I have blogged before about my conviction that the sea reflects the colour of the sky, hence the blue. But that doesn't explain the green. Then I noticed that two rivers flow out into the sea in the bay.

My theory is that the large amount of freshwater from heavy rain flowing into the bay pushed the salt water further out. Also, the freshwater is less dense so would ride over the salt water. I saw a hint that green colouration could well be biological and due to algae or plankton. The salt water containing these was pushed further out and so the green colour was further out.

Preparing for Lower Sixth Physics #14: Single slit diffraction with a laser

I shone a laser at a wall. Note the circular dot on the wall (and ignore the reflection below it from the table top).

Then I fired the laser beam through the gap between 2 razor blades.

 

When the gap gets small enough, the beam gets spread out. Note that it does not spread out evenly but that there is a line of dots with blanks between them. This is just caused by a SINGLE slit.

When the slit is really narrow, the dots are stretched out even more sideways. Here you can see the central dot smeared out into a line and a very faint one to the right and to the left of it. Maximum spread is when the width of the gap is the same size as the wavelength. It this case, the wavelength is about 600 nanometres. That is 0.0006 of a millimetre. I don't think I got the razor blades quite that close together.

Here the razor blade gap was somewhere between that shown in the first two pictures.

 

A lovely day for drying the washing

Just in case you didn't know, tumble dryers are not the only way to dry the washing. There was a lot of free energy out there for the taking today. It was very windy but with a lot of warm sunshine at times. Things dry when the water in them evaporates. The infra-red thermal radiation from the sun is absorbed. This gives the water molecules more energy - energy enough to beat the surface tension forces holding the liquid together. The wind moves escaped water molecules away quickly meaning that the air around the washing is always dry. Air can only hold a certain amount of water vapour at any given temperature. Above that amount and the air becomes saturated, some of the vapour condensing back into liquid water - the opposite of what we want to happen. If the escaped water vapour molecules are moved away quickly by the wind, this does not happen. The warm day with the higher air temperature also helps in this regard too - at higher temperatures air can hold more water vapour before becoming saturated. Now I need to go away and remember what saturated vapour pressure is about.

A controlled experiment

I was fascinated to observe this allergy test. A strip is stuck on and 10 possible allergens are separately dropped on and poked into the skin. The ++ at the top is the control. On the left side it is histamine to show the way that chemical makes the skin come up in a welt. The control is needed to show that the skin really does react to histamine. A negative control was placed on the right hand side. I didn't find out what it was, maybe antihistamine or perhaps just water. You can't tell because nothing happened to the victim. It is to show that the skin doesn't react to just anything. Now compare the welt at 4 in the top picture with the control. Allergen 4 must be provoking the body to produce histamine and that is an allergic reaction. It is a great example of a controlled experiment. It's not a technique used in Physics. I'm struggling to think of an example. You can't have a control Universe to measure our Universe against!

Differential weathering on Hilbre Island

Hilbre Island is one of a line of three odd lumps of sandstone in the middle of the Dee Estuary on The Wirral, between Liverpool and North Wales. I was fascinated by the way that some layers had weathered more than others. The layers are very thin. I wonder what long length of time they represent. They are a nice desert sandstone from when we were as far north as the Sahara is now. Wigton is made of similar sandstone. But look at the layers in the top photograph. Why have some resisted weathering more than others? There was no obvious change in composition. Is it that the "glue" holding the grains together was stronger at that time? I'm guessing that it will be some type of salt holding it but I've now got something to go away and look up.

British Summer Time in Rydal

This is the sundial outside Rydal church. It was taken when the Sun was highest in the sky so the sundial said 12 noon. However my watch said 1pm. British Summer Time. What I need to think about next time is whether an accurate watch set to Greenwich would be out by up to 15 minutes because we are west of Greenwich. This sundial didn't come with the graph like the one at Amble so I need to be more observant if I go again on a nice day.

Preparing for Lower Sixth Physics #13: Wave-particle duality

This display used to be in the Physics lab. It was set up to illustrate the Schrodinger's Cat story. About 100 years ago, it was thought that an electron was a particle. Experiments show this. This is what you are taught at GCSE. Then more experiments were done that showed that it behaved like a wave. So what is it really? In Physics, wave and particle are diametrically opposite ideas. Particle is about position and wave is about movement. Schrodinger wanted to explain clearly that a wave couldn't be both. He said that they are as opposite as alive and dead. You can't be both alive and dead. The story can be told in a more complicated way that specifies the random mechanism, but let's simplify it by saying that a hypothetical cat is put into an opaque box which has poison in it and that conditions are rigged so that there is exactly a 50% chance that the cat will eat the poison and die. You go to the box, as seen below. You can't see in so is the cat alive or is it dead? Schrodinger said that logically the cat must be 50% alive and 50% dead since chance comes into it. This is impossible so an electron must be either a wave or a particle. He favoured the wave idea. However, others have used the story to explain that we don't really know what an electron really is. we just have these two human-made ideas: wave and particle. The electron is in a state of uncertainty as far as we are concerned until we do an experiment to investigate. The design of the experiment will fix the probability of whether we find a wave or a particle. The state of uncertainty is called the wave-particle duality. Physicists have probed the nature of reality and discovered that there are limits to what we can know. In one sense, the truth is not out there!

Time in Amble

This is the giant sundial in Amble on the Northumberland coast. I have posted about it before but have now spotted that it says that midday at Amble is 6 minutes and 17 seconds behind GMT. This means that Amble is 1.6 degrees west of the Greenwich Meridian. Also note the wavy correction graph that goes from sundial time to clock time. Part of this is a constant correction due to the 1.6 degrees west but the rest is due to the position of the Sun in the sky as the seasons change. I learned about analemmas this year and it must explain this graph. see http://apod.nasa.gov/apod/ap131222.html. I also found out that there is a different type of sundial called an analemmatic sundial. I think this is what I've encountered at Seascale on the Cumbrian coast but more on that later. http://en.wikipedia.org/wiki/Analemmatic_sundial

Contemplating the Universe in a big tent in Keswick

I was sat in this big tent in Keswick and was thinking that the Universe is actually a surface like the walls of the tent. However, the tent is a 2D surface inside a 3D world. String theory suggests that the Universe might be an 11D surface but not inside anything. So when the Universe expands, it is not expanding into anything. That takes some thinking about. And if the Universe is a surface, we must be on the edge of the Universe. A surface has no inside.