. Radiotherapy and phototherapy : including radium and high-frequency currents, their medical and surgical applications in diagnosis and treatment ; for students and practitioners . the heat, and at a small dis-tance from the centre the defi-nition is very little affected,while the heat falls off in amarked degree. It is only essential that thepoint of radiation be keptsmall in the tubes that are for use in diagnosis and radiog-raphy; the tubes that are for therapeutic use need not beso accurate in this detail. If the point be not so small, thenumber of parallel rays over a given area will be
. Radiotherapy and phototherapy : including radium and high-frequency currents, their medical and surgical applications in diagnosis and treatment ; for students and practitioners . the heat, and at a small dis-tance from the centre the defi-nition is very little affected,while the heat falls off in amarked degree. It is only essential that thepoint of radiation be keptsmall in the tubes that are for use in diagnosis and radiog-raphy; the tubes that are for therapeutic use need not beso accurate in this detail. If the point be not so small, thenumber of parallel rays over a given area will be greaterand the tube consequently more efficient. The size of thearea over which the cathode rays act upon the anode maybe determined by observing the gradually heating up. Thesmall area referred to will heat up first; or it may beobserved on the screen by interposing a sheet of thick lead-foil having a minute pinhole punched in the centre. The Angle of Greatest Intensity. It is generally supposedthat the rays at the target radiate into space in every direc-tion equally, and that the rays are given off in the mannerindicated in Fig. 26. It is known that the rays at the margin. Water-cooled regulating tube. APPARATUS 81 of the hemisphere of the total rays that are emitted by thetarget are weaker or less in number than at the line normalto the centre of the target. Now, it has been shown thatthe rays from a surface are stronger at the centre, and falloff or decrease^ as the angle of the ray to that of the centralray increases. It has been further shown that the strengthof the light decreased as the cosine of the angle and therelative strength of the light at any point is roughly shown Fig. 26.
Size: 1223px × 2044px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyork, bookyear19
