No diffraction on Pike O'Blisco

An oddity on the summit of Pike O'Blisco was strong mobile phone signal on one end of the summit gully and no signal 5 metres away at the other end. The summit rocks might be 10 metres high. They seem to block the electromagnetic waves. Waves diffract around objects that are the same size as the wavelength. The average mobile phone wavelength in the UK is 30cm http://www.creative-science.org.uk/mobile_LED.html The summit rock is much bigger than this. The waves cannot diffract around them.

Pool thermometer

I'm interested in how this pool thermometer works. I'd blithely assumed an electronic sensor. But it is a dial. That might actually be a coiled bimetallic strip. The idea there is that as the temperature rises, one metal expands more than the other and thus the strip uncoils. If a needle is attached to the coil, it goes round the scale.

Polarised windows in IJmuiden

I posted last month about polarisation patterns in train window glass. I wasn't sure how it was possible with only one polarising filter. On the ferry going into Amsterdam, I noticed that looking towards the Sun there was no polarisation pattern but looking at right angles to the Sun, there was a pattern (bottom photograph). That suggests that polarised light from the sky is acting as the first polarising filter.

Green through the glass

These are two views of a glass television table. It was about 2cm thick and 75cm long. The top picture is looking down through the glass. You can hardly see it. There is a green strip along the top of the lower photograph. That is looking endways on into the glass. Glass contains some iron impurities. The iron ions absorb at the red and the blue ends of the spectrum so only the green gets through. It happens along the length because a lot of ions are needed to make the effect noticeable.

Organ pipe in Cologne Cathedral

Here's the organ loft at Cologne Cathedral. I estimate the length of the biggest pipe as 5 metres based on the height of the balcony rail. Assuming an organ pipe to be a closed end pipe, that represents 1/4 of a wavelength. Wavelength would be 20 metres. Frequency = speed/wavelength = 330/20 = 16.5Hz. Problem is that it would be below the frequency that humans can hear!

Inertia on the power lines: Neandertal

We were on the Autobahn crossing the Neandertal. I was interested that there were concrete blocks hanging below the insulators. I have not seen that in the UK. I am guessing that there are cross winds. The inertia of the mass makes the wind less likely to move the lines. There do not seem to be the metal hammer end rockers on the wires that are used in the UK.

Polarised views en route to Mönchengladbach

Here's the view of the Autobahn. In the top photograph, light from outside is transmitted through the windscreen. It hits the dashboard and is reflected upwards. The reflected light hits the windscreen. There is a partial reflection in my direction. The bottom photograph with a polarising filter shows no reflection, so that light reflected back from the windscreen must be polarised. The angle of reflection must have been above the Brewster angle. I think this is 57 degrees for glass. I thought it looked 45 degrees just sat in the car but perhaps I didn't look closely enough. For the record, I was in the passenger seat! I was a UK registered car...