PSEA Educational Aids

This kids art table with storage is an ideal proposition for your toddlers to learn creativity. Learning by entertainment is always the best way, now enabled by this handmade set.

This equipment is used to determine the temperature at which a sample of bituminous material loaded by a 9.5mm diameter steel ball drops a specified distance when heated under specified conditions. The Ring and Ball Apparatus has a magnetic stirrer with adjustable heating facility and digital display of temperature.

An anatomical model is a three-dimensional representation of human or animal anatomy, used for medical and biological education.

A bell jar is a glass jar, similar in shape to a bell, and can be manufactured from a variety of materials (ranging from glass to different types of metals). Bell jars are often used in laboratories to form and contain a vacuum. It is a common science apparatus used in experiments.[1] Bell jars have a limited ability to create strong vacuums; vacuum chambers are available when higher performance is needed. They have been used to demonstrate the effect of vacuum on sound propagation.

In addition to their scientific applications, bell jars may also serve as display cases or transparent dust covers. In these situations the bell jar is not usually placed under vacuum

Around 165 CE, Ptolemy described in his book Optics a rotating potter's wheel with different colors on it. He noted how the different colors of sectors mixed together into one color and how dots appeared as circles when the wheel was spinning very fast. When lines are drawn across the axis of the disc they make the whole surface appear to be of a uniform color. "The visual impression that is created in the first revolution is invariably followed by repeated instances that subsequently produce an identical impression. This also happens in the case of shooting stars, whose light seems distended on account of their speed of motion, all according to the amount of perceptible distance it passes along with the sensible impression that arises in the visual faculty."[3][4]

Porphyry (c. 243 – c. 305) wrote in his commentary on Ptolemy's Harmonics how the senses are not stable but confused and inaccurate. Certain intervals between repeated impressions are not detected. A white or black spot on a spinning cone (or top) appears as a circle of that color and a line on the top makes the whole surface appear in that color. "Because of the swiftness of the movement we receive the impression of the line on every part of the cone as the line moves."[5] in the 11th century Ibn al-Haytham, who was familiar with Ptolemy's writings, described how colored lines on a spinning top could not be discerned as different colors but appeared as one new color composed of all of the colors of the lines. He deducted that sight needs some time to discern a color. al-Haytam also noted that the top appeared motionless when spun extremely quick "for none of its points remains fixed in the same spot for any perceptible time".[6]

Newton's primary colours
On 6 February 1671, Isaac Newton wrote a paper about the experiments he had been conducting since 1666 with the refraction of light through glass prisms. He concluded that the different refracted rays of light – well parted from others – could not be changed by further refraction, nor by reflection or other means, except through mixture with other rays. He thus found the seven primary colors red, orange, yellow, green, blue, "a violet-purple" and indigo. When mixing the coloured rays from a prism, he found that "the most surprising and wonderful composition was that of whiteness" requiring all the primary colors "mixed in a due proportion".[7]

In reaction to Robert Hooke's criticism of the new theory of light, Newton published a letter in the Philosophical Transactions in 17, with other experiments that proved how sunlight existed of rays with different colours. He described how the cogs or teeth of a gyrating wheel behind a prism can block part of the light so that all the colours would be projected successively if the wheel turns rather slow, but how all the colours will be mixed into white light if the wheel turn very fast. He also pointed out that rays of light that were reflected from multi-coloured bodies were weakened by the loss of many rays and that a mixture of those rays would not produce a pure white, but a gray or "dirty" colour. This could be seen in dust, which on close inspection would reveal that it consists of many coloured particles, or when mixing several colours of paint. He also referred to a child's top which would display a "dirty" colour if it was painted in several colours and made to spin fast by whipping it.[8]

After presenting his conclusions about dividing sunlight into primary colors and mixing them back together into white light, Newton presented a color circle to illustrate the relations between these colors in his book Opticks (1704).[9]

Many modern sources state that Isaac Newton himself used a spinning disc with colored sectors to demonstrate how white light was actually the compound of the primary colors.[10][11][12] However, these do not reference any historical source.

According to Joseph Plateau the first to describe how a spinning disc with Newton's seven primary colours would show an (imperfect) white colour was Pieter van Musschenbroek in 1762.[13]