p-ISSN 2089 – 0133 e-ISSN 2477-6416 Indonesian Journal of Applied Physics (2021) Vol.11 No.2 halaman 248 Oktober 2021 PENGUKURAN INDEKS ULTRAVIOLET MATAHARI DAN ATENUASINYA OLEH BEBERAPA BAHAN UNTUK REKOMENDASI WAKTU AMAN BERJEMUR Sigit Ristanto 1,* , Choirul Huda 1 , dan Affandi Faisal Kurniawan 1 1 Prodi Pendidikan Fisika, Fakultas MIPATI, Universitas PGRI Semarang, Semarang *sigitristanto@upgris.ac.id Received 02-07-2021, Revised 20-08-2021, Accepted 07-09-2021, Published 01-10-2021 ABSTRACT Research has been carried out on the measurement of the sun's ultraviolet (UV) index and its attenuation by several materials. This research was motivated by the need to bask in the hot sun as an effort to increase the body's immune system amid the Covid-19 Pandemic. The ultraviolet index is the key in determining the right time. This study aims to obtain data on the distribution of the UV index in an area and its attenuation for the purpose of recommending a safe time for sunbathing. The measuring instrument used is an analog UV index sensor that converts UV radiation into analog voltage in the range 0 – 1 V. The output value is read using a multimeter and then converted into UV index using the product's built-in conversion table. The UV index measurement is divided into three conditions, first based on the time range from 08.00 – 16.00 WIB, the effect of cloud cover, and the UV index measurement when passing through several materials: transparent glasses, ribbed glasses, plastic packaging, hats, and sports t-shirts. The results showed that the distribution of the UV index based on the time span was successfully obtained, cloud cover caused a decrease in the UV index by 4 levels and the attenuation of the UV index by several materials was obtained. Based on the sample data collection in Tinjomoyo Banyumanik, Semarang City, the safe time for sunbathing is in the range before 10.00 WIB and after 14.00 WIB. Keywords : UV index, ultraviolet protection, sun safe, solar radiation. ABSTRAK Telah dilakukan penelitian tentang pengukuran indeks ultraviolet (UV) matahari dan atenuasinya oleh beberapa bahan. Penelitian ini dilatarbelakangi oleh kebutuhan berjemur di tengah terik matahari sebagai upaya meningkatkan imun tubuh ditengah Pandemi Covid-19. Indeks ultraviolet menjadi kunci dalam menentukan waktu yang tepat. Penelitian ini bertujuan memperoleh data distribusi indeks UV di suatu wilayah beserta atenuasinya untuk keperluan rekomendasi rentang waktu aman berjemur. Alat ukur yang digunakan berupa sensor indeks UV analog yang mengubah radiasi UV menjadi tegangan analog pada rentang 0 – 1 V. Nilai output dibaca menggunakan multimeter lalu dikonversi ke dalam UV indeks menggunakan tabel konversi bawaan produk. Pengukuran UV indeks dibagi menjadi tiga kondisi, pertama berdasarkan rentang waktu pada rentang waktu dari pukul 08.00 – 16.00 WIB, pengaruh tutupan awan, dan pengukuran UV indeks saat melawati beberapa bahan: kacamata transparan, kacamata riben, plastik kemasan, topi, dan kaos olahraga. Hasil penelitian menunjukkan distribusi indek UV berdasarkan rentang waktu berhasil diperoleh, tutupan awan menyebabkan penurunan indek UV sebesar 4 tingkat dan atenuasi Indek UV oleh beberapa bahan berhasil diperoleh. Berdasarkan sampel pengambilan data di Tinjomoyo Banyumanik Kota Semarang diperoleh waktu aman berjemur berada pada rentang sebelum Pukul 10.00 WIB dan setelah Pukul 14.00 WIB. Kata kunci: indeks UV, proteksi ultraviolet, aman berjemur, radiasi matahari .