Hemsing was born on February 15, 1988, in Valdres, in a mountainous region of Norway noted for the presence of strong folk traditions. Her younger sister Eldbjørg Hemsing is also a violinist. Ragnhild took up the violin at age five. She studied at the Barratt Due Institute of Music in Oslo, one of Norway's top music schools, and by 14, she had given her concert debut, playing Mendelssohn's Violin Concerto in E minor, Op. 64, with the Bergen Philharmonic Orchestra and soon after that with the Trondheim Symphony Orchestra. Between 2003 and 2006, she won several major prizes, two of them Europe-wide. As a teen, she performed with Norway's major orchestras, and a connection with conductor Neeme Järvi, who has been active in Bergen, helped her broaden her reputation beyond Norway. She was invited to perform with Järvi conducting the Estonian National Symphony Orchestra and, in 2011, recorded Johan Halvorsen's Fossegrimen Suite on a Järvi album of that composer's orchestral works. She continued her studies with Boris Kuschnir in Vienna.
Hemsing made her solo recording debut that same year with YR, an album that contained Norwegian traditional music as well as a sonata by Edvard Grieg. The title referred to a work by composer Lasse Thoresen; that work has also become a Hemsing specialty that she has performed in a choreographic setting by Hallgrim Hansegård. In 2011, Hemsing also recorded the folk album Varde, which also featured Eldbjørg Hemsing and the folk ensemble Kvarts. The two sisters collaborated on music for a one-hour television documentary about the life of star 19th century violinist Ole Bull. Hemsing was signed to Norway's 2L label, a natural home for her in that the label has specialized in recordings that fuse classical and folk influences. She released her first album for 2L, Northern Timbre, in 2017; it featured works by Grieg, Sibelius, and Nielsen. She recorded the album Beethoven's Testaments of 1802 for 2L before moving to Berlin Classics and issuing the album Røta, which featured both violin and Hardanger fiddle, in 2021. She returned the following year on that label with an adaptation of Grieg's Peer Gynt, Op. 23, that used both instruments and drew on the folk influences in Grieg's original score. ~ James Manheim, Rovi