A uniform rope of length L and mass m 1 , hangs vertically from a rigid support. A block of mass m 2 is…

A uniform rope of length L and mass m1, hangs vertically from a rigid support. A block of mass m2 is attached to the free end of the rope. A transverse pulse of wavelength λ1 is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is λ2. The ratio λ2λ1 is:
  1. m2m1
  2. m1+m2m2
  3. m1m2
  4. m1+m2m1

Solution

The situation in the rope is given below,

The velocity of the wave at the bottom of the rope is given by,

v=Tμ; where T is tension and μ is linear mass density of the string.

v1=m2gLm1

Hence, the wavelength for frequency f will be,

λ1=v1f=1fm2gLm2

Similarly, at top the velocity will be,

v1=(m1+m2)gLm1

And, the wavelength will be,

λ2=1f(m1+m2)gLm1

Hence, the ratio of both wavelengths will be,

λ 2 λ 1 = m 1 + m 2 m 2 .

Asked in: NEET 2016 (Phase 1)

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