## Grote Wolk, 1995, JCJ VANDERHEYDEN

JCJ VANDERHEYDEN – Grote Wolk

## Untitled, 1989, Zoe Leonard

Zoe Leonard, Untitled, 1989, Silbergelatine-Abzug, Unikat, 25,4 x 20,3 cm, © Zoe Leonard und Galerie Gisela Capitain, Köln.

## Robert Ryman

“In my studio I see the paintings with daylight from above, on cloudy and sunny days, and in incandescent light, in various strengths, without daylight. It is not just the intensity of the light, but the direction of the source that is important, and in each light situation the paintings looked different. At one point, I thought I would not be able to show the paintings because I could not know how they would look. How is someone going to know how the paintings work with light? However, I quickly got over that. Paintings don’t have much meaning unless they go out into the world”.

## Doppler effect – Wikipedia, the free encyclopedia

The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.

## Interference (wave propagation) – Wikipedia, the free encyclopedia

The principle of superposition of waves states that when two or more propagating waves of same type are incident on the same point, the total displacement at that point is equal to the pointwise sum of the displacements of the individual waves. If a crest of a wave meets a crest of another wave of the same frequency at the same point, then the magnitude of the displacement is the sum of the individual magnitudes – this is constructive interference. If a crest of one wave meets a trough of another wave then the magnitude of the displacements is equal to the difference in the individual magnitudes – this is known as destructive interference.