X-rays simply explained : a handbook on the theory and practice of radiography / by R.P. Howgrave-Graham.

Date:
[1903?]
Catalogue details

Licence: Public Domain Mark

Credit: X-rays simply explained : a handbook on the theory and practice of radiography / by R.P. Howgrave-Graham. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    becomes so rapid that the colours arc blended and undistinguishaUr. The same thing is sometimes done with the vanes of the little wheel mentioned immediately above. Heating Effect,—One other experimental proof of the violent nature of the molecular bombardment from the kathode, is given by the tube illustrated in fig. 4, Plate I. The kathode is a large cup of aluminium, the use of which must be explained first. It has been shown that the molecules thrown off from the kathode follow paths nearly at right angles to its surface (the word nearly is used because in ordinary Crookes' tubes this rule holds good to a fairly approximate degree, though it ceases to be true when X-ray vacua are reached). Now it is clear that if radiant matter is proceeding from the whole interior surface of a cup-shaped kathode in straight lines normal to that surface, there must be a kind of focus where the lines meet or are concentrated. This focussing effect, both in ordinary Crookes'' tubes and in X-ray tubes must not be confused with the reflection, of parallel beams of light, heat, sound or Hertz waves by parabolic or spherical mirrors. The case in question is not one of reflection, for the rays actually come into being at the surface of the cup. To the edge of the cup, fig. 4, Plate I., a small piece of platinum or platinum-iridium foil is attached by an upright support so that it lies just in the focus of the kathode stream. When the discharge is