Question: what are cardinal points of a thick lens
[{'answer': 'focal points', 'provenance': [{'wikipedia_id': '4268332', 'title': 'Cardinal point (optics)', 'start_paragraph_id': 1, 'start_character': 167, 'end_paragraph_id': 1, 'end_character': 179, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'principal points', 'provenance': [{'wikipedia_id': '4268332', 'title': 'Cardinal point (optics)', 'start_paragraph_id': 1, 'start_character': 185, 'end_paragraph_id': 1, 'end_character': 201, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'nodal points', 'provenance': [{'wikipedia_id': '4268332', 'title': 'Cardinal point (optics)', 'start_paragraph_id': 1, 'start_character': 211, 'end_paragraph_id': 1, 'end_character': 223, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '4268332', 'title': 'Cardinal point (optics)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 856, 'bleu_score': 0.9850176677359421, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 884950106067009882}, 'section': 'Section::::Abstract.'}]}]