Sunday, 26.09.2010

Flüssiger Sauerstoff fließt an einem Magneten vorbei.

### How fast is the rotor of a Helicopter

Tuesday, 16.02.2010

With an exposure time of 1/100s and a roto diameter of 11m one estimates about 220m/s for the speed of the blade tips.

One often reads again that the blade tip of a helicopter reaches supersonic speed (over 340m /s). In hover, this is not the case for this helicopter. The helicopter, Eurocopter BK117-C1 has a rotor diameter of 11m. During the exposure time of 1/100s the tips moved about 2.2 meters. The rotor moves at approximately 220m /s and turns nearly 7 times per second.

### Defraction limit using a digital camera

Tuesday, 24.11.2009

Die Auflösung eines Objektivs ist beubungsbegrenzt von der Blende abhängig.

In the picture you can see small sections (about 100 pixels wide) of a photograph that was taken with a 50mm lens from a distance of 5m from a laptop screen. We see significant uncertainty in the larger aperture numbers (22). The lower quality in Aperture 1.8 is due to other aberrations.

Due to the diffraction limit the diameter of a pixel is d = 2.44 · ? · B, where F-number B and the wavelength ? determined. With a typical value of ? = 555nm we obtain d = B · 1.3?m. The typical pixel size of today's digital SLR cameras is about 5?m, so that we reached at f / 4, the theoretical limit. Digital Cameras have in some cases significantly smaller pixel sizes because they work with smaller image sensors.

### Polarized light in nature

Wednesday, 14.10.2009

There is more polarized light than you think

The 20 regular readers are probably a little tired of the polarization, but the big difference between horizontally and vertically polarized light at a normal view I was not aware of. The sun was low, and about 90 degrees to the left of the view direction. The sunlight is therefore scattered in the mist by approximately 90 degrees. In this case, the polarization can only be perpendicular to the direction of incidence and outgoing beam. Therefore in the picture it is almost vertically. Both images were taken with the same aperture and shutter speed. To get an idea of where polarized light appears in the picture, I have determined the difference with the GIMP. In the fine structures in the tree, the leaves probably did not stay exactly in the same place. The brightness at this positions are probably artifacts.

Here the difference between vertically and horizontally polarized light is shown

In landscape photography you should always have a polarizing filter it.

### 3D glasses contain a lot of physics

Thursday, 1.10.2009

Polarisation of a LCD display'>linear polarisierten Licht des LCD Bildschirm gleich, wenn die Seite mit dem linearen Polarisationsfilter in Richtung des Bildschirms zeigt. Für einen 3D Effekt wären die Brillen so natürlich nicht geeignet, da hierbei jedes Auge ein anderes Bild "sehen" soll. Im nächsten Bild erzeugt die "falsch" herum gehaltene Brille am großen Pferd zirkular polarisiertes Licht, beide Gläser in unterschiedlicher Drehrichtung. Das Licht des unteren Brillenglases wird von der vorderen Brille blockiert, das des oberen Brillenglases durchgelassen.

Die Brille wird im 3D Kino zirkular polarisiert verwendet.

In dem aktuellen Wikipedia Artikel werden diese 3D Brillen übrigens  noch nicht behandelt. Vielleicht findet sich jemand, der diese Brillen in dem Wikipedia Artikel ergänzt! In jedem Fall lohnt es sich beim nächsten Kinobesuch mit den Brillen ein wenig zu experimentieren.[/lang_de]

Used in the wrong direction the 3D eyeglasses blocks linear polarized light of the LCD display.

Modern 3D eyeglasses consists of circular polarisation filters. These filters have on the one side a normal linear polarisation filter and on the other side a ?/4 plate. Therefore both glasses of the eyeglasses behave in linear polarized light LCD of the screen directly, if the side with the linear polarisation filter shows toward the screen. For a 3D effect the eyeglasses would not be suitable, since here each eye has to see another picture. In the next picture the eyeglasses held at the large horse produce circular polarized light, both glasses in different direction of rotation. The light of the lower eyeglass lens is blocked due to the front eyeglasses and let through that of the upper eyeglass lens.

The glasses for 3D cinema use circular polaized light.

[/lang_en]

### Polarisation of a LCD display

Monday, 14.09.2009

Foto with polarisation filter

Foto of a LCD display using a polarisation filter. By putting a transparent paper on top of the screen, the polarisation is broken and the display can be seen. Parts without transparent paper are dark due to the polarisation filter.

### Luminescence of envelopes

Sunday, 13.09.2009

Opening of an envelope with liminescence

The splice of an envelope is lightning due to luminescence. The foto was exposed 0.1s and the envelope was lying at the table during the other site of the splice beeing moved up.

### The moon, always a nice foto

Monday, 7.09.2009

The moon fotographed with a 300mm lense

A simple 300mm lense is enough to see a log of details of the moon at a distance of more than 300000km.

### How fast is a rain drop falling?

Saturday, 5.09.2009

How fast is a rain drop falling?

The foto was exposed with 1/500s. The hight of the foto is about 20cm. This means that the velocity is about 25m/s. The rule: velocity in m/s is 6 times the diameter in mm seems to fit.

### Free fall illuminated with neon light

Sunday, 30.08.2009

Freier Fall

The foto was taken with 1/3s exposure. As the neon light flickers at a frequency of 100Hz on sees the falling white object with interruptions.

### Interference at a spider net

Sunday, 16.08.2009

Interference at the thin threads of the spider net

Interference at the thin threads of the spider net.