In 1911, Geiger and Nuttall discovered an empirical relationship between the half-life of alpha decay and the energy of the emitted alpha particles.

1. In 1962, Harry Hammond Hayes published 'The History of Ocean Basins'.

2. In this, the theory of plate tectonics was outlined and which was later also known as 'ocean bottom spreading'.

Explanation: Most communication waves cannot transmit data accurately over long distances due to the curvature of the earth. They can only do so in the line of sight. However, they are not reflected by the ionosphere like radio waves and can be relayed to a wide area using geostationary satellites.

A potentiometer is an accurate and versatile device to make electrical measurements of emf because the method involves a condition of no current flow through the galvanometer, the device can be used to measure potential difference, internal resistance of a cell and compare emf's of two sources. Q.