
	E-mail us at helicon@rm.com or telephone us on 08450 700300.


	Looking for help with one of our CD-ROM products? Visit our technical support section.

Data sets and samples

Subjects | Fact sheet | Samples

Educational resources: Sample images

Gothic architecture

A cutaway of a Gothic cathedral.

(Image © Helicon)

eye

The human eye. The retina of the eye contains about 137 million light-sensitive cells in an area of about 650 sq mm/1 sq in. There are 130 million rod cells for black and white vision and 7 million cone cells for colour vision. The optic nerve contains about 1 million nerve fibres. The focusing muscles of the eye adjust about 100,000 times a day. To exercise the leg muscles to the same extent would need an 80 km/50 mi walk.

(Image © Helicon)

atomic structure

The structure of a sodium atom. The nucleus is composed of 12 protons and 11 neutrons. Eleven electrons orbit the nucleus in 3 orbits: 2 in the inner orbit, 8 in the middle, and 1 in the outer.

(Image © Helicon)

integrated circuit

An integrated circuit (IC), or silicon chip.

(Image © Helicon)

cloud

Standard types of cloud. The height and nature of a cloud can be deduced from its name. Cirrus clouds are at high levels and have a wispy appearance. Stratus clouds form at low level and are layered. Middle-level clouds have names beginning with 'alto'. Cumulus clouds, ball or cottonwool clouds, occur over a range of height.

(Image © Helicon)

seed drill

English agriculturist Jethro Tull invented the mechanized seed drill in about 1701. The sowing of seeds in uniform rows allowed weeding between the rows of seedlings during growth, so improving the yield. Previously seeds had been broadcast by hand across the land.

magnetic-ink character recognition

An example of one of the uses of magnetic ink in automatic character recognition. Because of the difficulties in forging magnetic-ink characters, and the speed with which they can be read by computer systems, MICR is used extensively in banking.

graphs of simple functions

When a quadratic expression is plotted on graph paper and the points are joined smoothly, the resulting shape is a U-shaped curve (a parabola). Where the x² expression is negative, as in y = 3 – x², the parabola is inverted. The graph of a cubic function can have between one and three bends in the curve. In a reciprocal function, as the value of x gets close to 0, y becomes infinite. As x gets very large, y gets very small but never reaches 0.

counterpoint

An example by Bach of double counterpoint. The second system reverses the position of each line.

refraction

The refraction of light through glass. When the light ray strikes the glass (a denser medium than the air) it is bent towards the normal. When it leaves the glass and re-enters the less dense medium it is bent away from the normal.