The instrument used to measure the duration of sunshine is the

The instrument used to measure the duration of sunshine is called the **campbell-stokes recorder**. This instrument is specifically designed to measure the amount of sunlight received at a particular location over a given period of time. The campbell-stokes recorder consists of a glass sphere that is mounted in a metal frame. This sphere acts as a lens, focusing the sunlight onto a specially designed card or paper underneath. The card or paper is positioned in such a way that it is slightly above the focal point of the lens. When sunlight passes through the lens and focuses on the card, it causes the card to heat up. As a result, a burn mark or a scorch is left on the card. By measuring the length of the burn mark, we can determine the duration of sunshine. The campbell-stokes recorder is widely used in meteorology and climatology to monitor and document the amount of sunshine received in a given area. It is a simple and effective instrument that provides valuable data for studying weather patterns, climate change, and solar energy potential. In conclusion, the instrument used to measure the duration of sunshine is the campbell-stokes recorder, which uses a glass sphere to focus sunlight onto a card or paper and measures the length of the resulting burn mark.