Kitchen optics

An everyday kitchen can provide ample opportunities for observing optical phenomena, and as Mónika Landy-Gyebnár and Ágnes Kiricsi are not only good housewives but keen observers of such beauties, they always keep their eyes open for a chance of photographing something interesting while doing their household duties.

When you decide to drink your coffee in the early morning sunlight that just reaches your kitchen window, you might be lucky to get its steam of equal droplet size, and opening your eyes with the first sip of coffee you notice the colours of the drifting steam. You must have another sip to be sure that you really see the scattered sunlight and the display of iridescent colours.





If you use a spoon to stir your coffee with, don't run to the dishwasher immediately, but be a bit negligent, and wait till the coffee dries on it.


You may discover spectral colours again: patterns of thin film interference. Could it be the coffee's volatile oils or bacteria signalling problems of mouth hygiene?

Bisquits are always good to crunch with the morning coffee. Most of them are packed in a small cellophane bag that we can easily drop aside at the table by the window. And here comes the sun again - as its rays fall on the empty sachet, birefringence produces the well-known spectral colours again.

Not only human beings need a refreshment in the morning - our plants are also thirsty. And not only cellophane sachets are prone to showing birefringence, but transparent plastic flowerpots, too.

We have to pack a sandwich for the workday, maybe a good slice of ham - oops, the ham is also showing the spectral colours! The tiny (a muscle cell is about 10-80 microns in diameter), regularly arranged cells of the meat behave like the water droplets of clouds.

When the office hours are over, we still have some activities at home: for example making dinner for the family. Let's treat them with some meat balls, fried delicious in hot rainbow-coloured oil. Yes, rainbow coloured, as the afternoon sun still shines in, and the transparent oil bottle is placed in front of the window. You don't necessarily need a usm filter (or a usm sieve :)) to see the caustic patterns.

But be careful! Never cover hot food with a foil, otherwise they might produce colours again. First spectral ones on the foil, which we are happy about, but later a sickly shade of green on the meat itself. In this second stage, don't hesitate to throw the food into the dustbin.

Towards the end of the day, the work of the housewife has not ended yet. She's still on duty in the kitchen, looking at the pile of dirty dishes that has been produced.While the hot water gathers in the sink, it also steams a bit. There's no evening without a good streetlamp corona - you only have to look outside for a moment! The hot vapour has precipitated on the cold glass of your kitchen window, so the long day's last phenomenon wishes you good night with a colourful display.

Let's hope that reading so much about these household duties won't cause you nightmares of mugs carelessly washed up, and that one evening a brave man sits in front of the computer, and writes an article about the optical phenomena observed during his weekend-long tinkering in the workshop.

Shadows on ice crystals

During the cold spell in the middle of January, some of us in Hungary started "experimenting" with snow crystals. As surface halos had been observed for several consecutive days (see the images of the odd radius surface halos by Ákos Ujj: 1 - 2 ), our basic idea was to find out whether we would see the trace of the 22 degree halo if we simply threw up the snow crystals covering the ground. Interestingly, the answer was yes. It was really exciting to observe that 22° from the sun, the crystals were glittering in spectral colours, and they faintly drew the form of the halo. Unfortunately, I was not so lucky with photographing the effect. All I could capture was the streetlamp casting its shadow on the crystals thrown and kicked in the air by Alexandra Farkas.

In the evening, however, Károly Vicián was much more successful. He had similar methods, but with longer exposure time, he did not only manage to photograph the shadow of the broom that was used to cover the spotlight, but the halo thus forming, too.

Perigee Moon

This photo was taken by Claudia Hinz at the evening of Jan. 11th, 19.35 CET from Mt. Wendelstein (1838m), Southern Germany. The full Moon in this night was extra bright. Dr. Elmar Schmidt of the SRH University of Applied Sciences in Heidelberg, Germany, used an absolutely-calibrated photometer to precisely measure the moonlight and found it more than 50% brighter than that of a typical full Moon.

1. The Moon was at perigee, the side of the Moon's elliptical orbit closest to Earth.

2. The Earth-Moon system was near perihelion, the side of Earth's elliptical orbit closest to the sun. Extra sunlight increased the reflected luminosity of the Moon.

3. The Sun-Earth-Moon trio were almost perfectly aligned. This triggered a strong opposition effect an intense brightening of the lunar surface caused by the temporary elimination of normal shadows.

4. The weather conditions were optimal for photometry due to the clean and dry arctic air (its relative humidity being less than 10% at the moment of the photo). This resulted in only clear air scattering of moonlight with no extraneous glare as evident in the completely blue night sky. The brightness of the mountain landscape was additionally increased because of the reflection from the snow.

Elmar Schmidt details the relative contributions of each factor in his full report.


Text: Elmar Schmidt & Claudia Hinz

Effects in cloud bows caused by perspective

In the morning of December 12, 2008, I coud observe a cloud bow on a stratocumulus layer, which was kind of perspectively cracked. Due to the ruggedness of the cloud surface it seemed as if there was a deep horizontal notch on the left side of the cloud bow.

But also this moonlight cloud bow, taken on September 9, 2008, seems to have vertical indentations and also an elliptical shape caused by the horizontal projection upon an uneven surface.

Sunset sequence

This sequence of images of the setting sun was taken on September 14th, 2008, from Beverly Beach, Oregon, on an evening when sea mist partly obscured the sun. A vague green colour appeared on the upper edge of only one or two of these images.

Author: Alan Clark, Calgary, Canada

Volcanic Twilights over Europe

On August 7, the Kasatochi Volcano, situated on the Aleutian Islands near Alaska, erupted. Clouds of ashes and sulfur dioxide were ejected up to 15 km into the stratosphere.

During the following 3 weeks, the volcanic clouds spread over the whole northern hemisphere, causing widespread intense twilight colours and often also crepuscular rays. These were first reported from Northern America during mid August, but at the end of the month, these "volcanic twilights" were also observed in Europe.

In the evening of August 29, several observers reported a strange and intense yellow light around sunset, followed by a purple light. Some of them were reminded of the unusual twilights between February 17 and 20, which were caused by PSC.

On August 30, skies were clear over Germany, and so many observers could see a kind of silvery cloud stripes a few minutes before sunset. These stripes were orientated north-south and at first glance looked like cirrus or cirrostratus clouds. But during the day these clouds had not been visible at all, and when looking at them carefully, one could see that they were higher than normal high clouds. The contrails of some airplanes were obviously below these clouds, and as the contrails turned reddish in the light of the setting sun, the clouds still remained bright. So they must have been floating higher up in the air, somewhere in the
Stratosphere.

After sunset, the clouds got a more brownish-yellow hue, but turned pink only about 20 minutes after sunset. Some observers also reported intense crepuscular rays. The purple light faded about half an hour after sunset.

In the morning of August 31, the colours and cloud stripes could also been observed. In the evening, a cold front with thunderstorms approached the western parts of Germany. While even the tops of the cumulonimbus clouds were already dark, the stratospheric clouds still lay in plain sunlight. That evening, instead of the regular stripes of the day before, they looked more like irregular waves.

During the first days of September, the strange twilight colours could still be observed over southern Germany, while for the rest of the country morning and evening skies looked quite normal again.

But as there are still volcanic ashes in the stratosphere, the colours may return. So keep watching the skies before sunrise and after sunset.

Author: Peter Krämer, Bochum, Germany

Glass Bead Rainbow on Kitchen Table

The observation of a rainbow in glass beads on, respectively next to, a fresh route-indicator in a street I made by chance made me think about studying the effect also in the light of a street lamp. But unfortunately the glass beads had been scattered too much by the traffic within a few days. However, also by chance, I learned that glass beads are also used for facing the surfaces of, for example, metal objects, and so I asked our precision tool maker to bring me some...and then I started the experiment.

As a source of light I used a small bulb like those you find in a bicycle lamp, but without a reflector, because the light source should be as similar to a single point as possible. I scattered the glass beads on a black eloxated aluminum sheet (ca. 30 x 40 cm), and the result was overwhelming. Exactly as in the experiment made by Christian Fenn, the bow can be studied under different geometrical conditions when using a laser and a rotating mirror. The easiest way is to realize the reversed geometry just as otherwise the shadow of the head would be rather large as distances are small. Just put the metal sheet on a table, hold the lamp above it and look at it using different positions of your head. I also took some photographs after having attached the lamp to a mounting. This also shields the direct light. The first supernumerary is also visible, and like in the rainbow caused by water, a polarisation of light can also be proved. (1 2 3)

Seen through a microscope, the glass beads look like this:


I estimated the average radius to be at about 50 micrometers with an average variation of about 15 micrometers. But there are different sizes available. Similar to water drops of that size, the colours are rather blurred (this is especially obvious when you look at a glass bow in sunlight). The spectrum of light coming from a bulb is also rather "red" which causes the strange colours of the pictures.

As I was very fascinated by that phenomenon, I also calculated some simulations using the Airy-theory for glass beads (I could reuse some parts of the original text about the twinned bow for this). And in order to show the phenomenon from the observer´s position, I could use the text on halos on snow covers (so after 10 years the circle is closed...). An imaginary depiction seen from above obviously shows the "intersection through the apple", but as far as I know, nobody tried to explain the different width of the colour bands up to now. Tis effect becomes very obvious when "opening the inner bow by merging with the outer one" (This is very difficult to describe; you must have seen it). However, the geometrical data of the simulation are not exactly the same as in my observation because I did not execute any measurements while photographing.

Left: Seen from above with the observer´s position in the centre of the picture
Right: Gnomonical projection from the observer´s position (“simulated photograph”)

Author: Alexander Haußmann, Hörlitz, Germany

Yellow Rainshower

On August 13, I could witness another atmospheric phenomenon in Bochum, Germany.

In the evening, about half an hour before sunset, a rainshower approached from the west. Behind the shower, the sky cleared up very rapidly, so that the low evening sun could shine through the veil of rain. This caused very strange light conditions I never experienced before.

First there was a yellow squall line visible, followed by a bright yellow veil of precipitation. As it came nearer, another shelfcloud-like structure passed from south to east. This cloud was also strangely illuminated and showed orange and brownish colours.

The squall line in the western and northwestern part of the sky turned more and more orange, too, while the rain got an intense and bright yellow. The whole landscape was bathing in a strange and intense yellow light with orange-coloured clouds above and in the east.

When it began to rain, a rainbow appeared in the east, visible as a full semi-circle. The blue part of the bow had already gone, only red, yellow and a faint green were visible.

Then the sun sank beneath the horizon, and all colours faded away within a few minutes. So there was no really red rainbow that evening, but nevertheless it had been very impressive to me.

Author: Peter Krämer, Bochum, Germany

Twinned Rainbow

On August 13, after a rainshower had passed over Bochum, Germany, a twinned rainbow appeared. The bow was rather faint, but the twinning in its upper part was clearly visible. The red and the yellow colour bands of the rainbow were twinned.

On photographs of the rainbow, the twinning effect is hardly visible, but after oversaturating one of the pictures, the twinning turned out well.

During the rainshower, large drops were falling. A second shower about half an hour later with normal-sized drops also produced a rainbow. Even though this bow was very bright, it was not twinned, but showed a secondary bow and supernumeraries.

This is another hint for the theory to be right that the effect of twinned rainbows is really produced by large raindrops getting flattened by the resistance of the air when falling.

Author: Peter Krämer, Bochum, Germany

Light refraction on Fireweed-seeds

While testing my new Tamron AFR70/300 on several plants and flowers I passed a very steep slope overgrown with fireweeds.The sun was relatively low above the slope that I noticed a silky lustre beetween the seeds. As more I was moving the plants beewenn me and the sun, the effect merged into an incredible refraction of light on the silky like seeds. I shot a few pictures and those which where slighty off focus showed very bright colours. This effect seems to be similar with light refraction on spider-webs. In this case though colous where extremely bright.

More pictures: 1 2 3 4 5

Author: Rolf Kohl, Germany