In 1894, toymaker Mr. C.E. Benham discovered that a spinning disk with a particular pattern of black and white marks could cause people to see colors.

Benham's top, also called Benham's disk, is named after the English toymaker Charles Benham, who, in 1895, sold a top painted with the pattern

On the right the .Benham Disk. spins, initially quite slowly. Click repeatedly on the appropriate button to change rotation speed or direction.

Structural colors are colours which are caused by interference effects rather than pigment.

Tyndall effect is usually applied to the effect of light scattering on particles in colloid systems, such as suspensions or emulsions. It is named after the Irish scientist John Tyndall.

Diffraction is when a wave goes through a small hole and has a flared out geometric shadow of the slit. Diffraction is a characteristic of waves of all types. We can hear around a corner because of the diffraction of sound waves. For instance, if a wall is next to you when you yell, the sound will parallel the wall. The wall may stop, but the voice doesn't; sound will almost turn the corner of the wall. This is diffraction.

Reflection is when waves, whether physical or electromagnetic, bounce from a surface back toward the source. A mirror reflects the image of the observer.

Refraction is when waves, whether physical or electromagnetic, are deflected when the waves go through a substance. The wave generally changes the angle of its general direction.

Wave Refraction at Jaws, Maui

Refraction is the bending of waves because of varying water depths underneath. The part of a wave in shallow water moves slowe

Refraction is the change in direction of a wave due to a change in its velocity. This is most commonly seen when a wave passes from one medium to another.

Huygens-Fresnel principle

moving test sinusoidal grating may be altered by adaptation to another moving grating whose direction

luminance gratings of spatial frequency f or 2f

spatial and temporal modulation of contrast on the visibility of sinusoidal gratings

Experiments with drifting gratings are widespread in the study of neurons in the retina

device for generating drifting grating patterns

Experiments with sinusoidal visual stimuli

data from drifting grating experiments

What is "Physical Optics"Physical Optics

---