JEE Advanced 2020 Full Test 4 Paper 1

A steel wire of length 60cm and area of cross A section 10−6m2 is joined with an aluminium wire of length 45cm and area of cross section 3×10−6m2. The composite string is stretched by a tension of 80 N. Density of steel is 7800kgm−3 and that of aluminium is 2600kgm−3. The minimum frequency of turning fork, which can produce standing wave in it with node at joint is