A lens that has lower power or ability to focus light sharply.

Figuratively describes a person or argument lacking strength or clarity.

कमज़ोर तर्क

English Usage: His weak lens on the subject made it difficult for him to convince the audience.

Hindi Usage: विषय पर उसका कमज़ोर तर्क दर्शकों को मनाने में कठिनाई उत्पन्न करता है।