One third of the 3rd level students in Ireland study a STEM subject, which include Physics and Mathematics.
Physicists often work in teaching, academia or research. Accessing publications in the field of physics is perfectly possible in English, but especially in academia and research you will be operating in an international setting where language skills are always useful. Existing degree courses in physics and languages illustrate the solid combination of a STEM subject and a foreign language. The official language of CERN is French, English being the other language used.
As a physicist you could also work in various industries involving engineering or laboratories. Graduate opportunities abroad will give you experience working with foreign teams, useful to have language skills. Space science is an exciting area where a physics background is required, and a foreign language enhances your career in this international sector.
Mathematics is used in for example engineering, technology, finance, statistics and data analysis. In these global industries it is beneficial to have language skills. Teaching is also an option, you could consider combining it with a foreign language. STEM subjects together with a foreign language give a strong skill set which says something about you : you have STEM skills but also master the tool - a foreign language - which truly makes you international, outward-looking and open to contacts far and beyond.
Data analysts and statisticians work with numbers, but vast job opportunities in big data may take you to work at projects anywhere in the world where you will also need words - in a foreign language.