A uniform thin rope of length \( 12 \mathrm{~m} \) and mass \( 6 \mathrm{~kg} \) hangs vertically from a rigid support a…

A uniform thin rope of length \( 12 \mathrm{~m} \) and mass \( 6 \mathrm{~kg} \) hangs vertically from a rigid support and a block of mass \( 2 \mathrm{~kg} \) is attached to its free end. A transverse short wavetrain of wavelength \( 6 \mathrm{~cm} \) is produced at the lower end of the rope. What is the wavelength of the wavetrain (in \( \mathrm{cm} \) ) when it reaches the top of the rope?

[JEE Main 2020, 3 Sep (Shift 1)]