Lesson Gallery

The Periodic Table Digital Illustration

In the late 19th century, Russian chemist Dmitri Mendeleev published his first attempt at grouping chemical elements according to their atomic weights. There were only about 60 elements known at the time, but Mendeleev realized that when the elements were organized by weight, certain types of elements occurred in regular intervals, or periods.
Today chemists officially recognize 118 elements and still use Mendeleev's periodic table of elements to organize them. The table starts with the simplest atom, hydrogen, and then organizes the rest of the elements by atomic number, which is the number of protons each contains. With a handful of exceptions, the order of the elements corresponds with the increasing mass of each atom

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A lesson in perspective

A lesson in perspective. Illustration shows a perspective view with the Eye of the Law at the vanishing point where the little ones shield the more important figures in the foreground; from small to large are the Weigher, Appraiser, Inspector, Superintendent, Manager, Trust Scapegoat, Government Scapegoat, Sugar Trust Director Don't Touch Sugar Trust it gave to Your Campaign Fund, and High Government Official Don't Touch Sugar. It gave to Our Campaign Fund'. Date 1909 December 15. A lesson in perspective. Illustration shows a perspective view with the Eye of the Law at the vanishing point where the little ones shield the more important figures in the foreground; from small to large are the Weigher, Appraiser, Inspector, Superintendent, Manager, Trust Scapegoat, Government Scapegoat, Sugar Trust Director Don't Touch Sugar Trust it gave to Your Campaign Fund, and High Government Official Don't Touch Sugar. It gave to Our Campaign Fund'. Date 1909 December 15

© Mary Evans Picture Library 2015 - https://copyrighthub.org/s0/hub1/creation/maryevans/MaryEvansPictureID/10607144

Physics experiment

Physics experiment. Screen display of the output from a physics experiment. The experiment involves monitoring changing position with time. The graph shows the position of an object (given as distance in metres) plotted against time (in seconds). The output is a wave of decreasing amplitude. Motion of this sort is seen in a damped oscillator, such as a mass bouncing on a spring, or the swinging of a pendulum. The gradient of the graph shows the velocity of the object. The velocity is zero at the peaks (the high points of a swinging pendulum) and at a maximum in between (the low point of the swing of a pendulum)

© ANDREW LAMBERT PHOTOGRAPHY/SCIENCE PHOTO LIBRARY