https://blog.gongquiz.com/2021/10/13/%ec%83%81%ec%9a%a9%ec%a3%bc%ed%8c%8c%ec%88%98-60hz-%ea%b5%90%eb%a5%98%ec%97%90%ec%84%9c-%ec%84%b1%ec%9d%b8-%eb%82%a8%ec%9e%90%ec%9d%98-%ea%b2%bd%ec%9a%b0-%ea%b3%a0%ed%86%b5%ed%95%9c%ea%b3%84-%ec%a0%84/