An apparatus shown below is used to investigate waves in a stretched string.

The wavelength of the wave shown in the diagram is measured as 120 cm120\text{ cm}120 cm. State what piece of apparatus is suitable for measuring this wavelength.
Write down the equation that links frequency, wavelength, and wave speed.
The string in the diagram vibrates at 35 Hz35\text{ Hz}35 Hz. Calculate the wave speed of this wave. Show your working.
The frequency of the signal generator is now decreased. This changes the wavelength of the wave, while the wave speed remains constant. Describe how the wooden bridge could be adjusted to show exactly one complete wave without changing the frequency back.
A student wants to investigate how the wavelength of a stationary wave on a stretched string depends on the frequency of the wave. Describe a method the student could use for this investigation.