Optical Note. 

 K. Takizawa. 



If one observes a Xewtoii's ring- apparatus through a thin film ni 

 mica, several sets of rings are seen in those parts of the field, where 

 if white light is used, ordinary Xewton's rings are not found. Each 

 group consists of a middle «lark ring with two concentric white rings 

 next the dark one, and several colored rings outside and inside. 

 Besides these prominent gT<3ups, a group of faint rings is observed 

 inside the first group. All sets are concentric with each other and 

 the space between any two sets is devoid of rings. The diameters ot 

 these rings depend on several conditions. The thinner the mica film, 

 tlie smaller the diameters. The greater the air film of the Xewton's 

 ring apparatus, the smaller the diameters. The effect of inclining 

 the film so as to receive the light from the Xewton's ring apparatus 

 more obliquely is equivalent to using a thinner film. All these 

 phenomena can be very easily explained by the ordinary elementary 

 theory of interferrence. 



As to the existence of these rings, it is well known that the rings 

 are invisible in those parts of the field, which correspond to a great 

 thickness of the air film, because the lio-hts of maximum and minimum 

 intensities are very nearly equal in their wave-lengths for a given 

 direction. If we examine a small portion of an <3rdinary Xewton's 

 ring (which is invisible in white light) by a prism, a large number of 

 dark bands are seen in its spectrum. If we bring the dark middle 

 ring of the first prominent, group as seen by a mica film (let us call 



