Moseley, after discussions with Bohr who was at the same lab (and who had used Van den Broek's hypothesis in his Bohr model of the atom), decided to test Van den Broek's and Bohr's hypothesis directly, by seeing if spectral lines emitted from excited atoms fitted the Bohr theory's postulation that the frequency of the spectral lines be proportional to the square of Z.
mˈoʊsli, ˈæftɚ dɪskˈʌʃənz wɪð bˈoʊɚ hˌuː wʌz æt ðə sˈeɪm lˈæb ænd hˌuː hæd jˈuːzd vˈændɛn bɹˈoʊks haɪpˈɑːθəsˌɪs ɪn hɪz bˈoʊɚ mˈɑːdəl ʌvðɪ ˈæɾəm, dᵻsˈaɪdᵻd tə tˈɛst vˈændɛn bɹˈoʊks ænd bˈoʊɚz haɪpˈɑːθəsˌɪs dᵻɹˈɛktli, baɪ sˈiːɪŋ ɪf spˈɛktɹəl lˈaɪnz ɪmˈɪɾᵻd fɹʌm ɛksˈaɪɾᵻd ˈæɾəmz fˈɪɾᵻd ðə bˈoʊɚ θˈiəɹiz pˈɔstʃʊlˈeɪʃən ðætðə fɹˈiːkwənsi ʌvðə spˈɛktɹəl lˈaɪnz biː pɹəpˈoːɹʃənəl tə ðə skwˈɛɹ ʌv zˈiː.