Contains reprints of the following research publications: i. "Thermionic Constants of Semi-Conductors" by K S Krishnan and S C Jain published in Nature, Volume 177, Issue 4502. It also contains a cut-out of the same. ii. "The Drude Dispersion Formula Shown to be Applicable to any Medium Irrespective of the Polarisation Field" by K S Krishnan and S K Roy, published in the Philosophical Magazine, Volume 1, Issue 10. iii. "The Polarization Field in an Ionic Crystal and its Influence on the Reststrahlen Frequency" by K S Krishnan and S K Roy, which was read at the Symposium on Physics of Solid State held during the Silver Jubilee session of the National Academy of Sciences. The paper is published in the Proceedings of the National Academy of Sciences (India), Allahabad, Volume 25, Section A, Part 2.