This diagram shows a stationary wave on a string.

(c) The frequency of the vibrator is doubled. Describe the changes in the stationary wave pattern.

A tuning fork that produces a note of 256Hz is placed above a tube that is nearly filled with water. The water level is lowered until resonance is first heard.

(b) The length of the column of air above the water when resonance is first heard is 31.2cm.

Calculate the speed of the sound wave.

(b) This diagram shows an experiment to measure the speed of a sound in a string. The frequency of the vibrator is adjusted until the stationary wave shown is formed.

(i) On a copy of the diagram, mark a node (label it N) and an antinode (label it A).

(a) Explain what is meant by:

(i) A coherent source of waves.

(a) Explain what is meant by:

(ii) Phase difference.

The speed $v$ of a transverse wave on a stretched wire is given by the expression $v\propto \sqrt{T}$

Where $\mathrm{T}$ is the tension in the wire.

A length of wire is stretched between two fixed point. The tension in the wire is $\mathrm{T}$. The wire is gently plucked from the middle. A stationary wave, of fundamental frequency $210 \mathrm{Hz}$, is produced.

The tension in the wire is now increased to $1.4 \mathrm{T}$. The percentage uncertainty in new tension is $8.0\%$. The length of the wire is unchanged. Calculate the new value for the fundamental frequency when the wire is plucked in the middle. Your answer must include the absolute uncertainty written to an appropriate number of significant figures.