However, Newton saw and reported on the bending of light around a needle and he also saw Newton's rings both of which we now know are due to diffraction and interference. Although Newton saw the phenomena of diffraction he did not recognize it. Here is an activity in which you can see Newton's rings for yourself. When you come to the Exploratorium visit the exhibit Chromatic Aberration. Here you will see that your eye cannot focus blue light and red light at the same time.
Human eyes bend blue light more than red light.
Most transparent things bend blue light more than red, this is known as dispersion. He did not patent his idea which would have required him to publish how it was done, instead he kept it secret, and so reserved the entire trade in achromatic lenses to himself for far longer than the patent would have. He made his achromatic lenses by combining two lenses with different dispersions. Modern lenses can focus three wavelengths at the same time, these lenses are called apochromats and were invented by Ernst Abbe in the 1860's. In 1801, Thomas Young passed light through two slits and observed interference.