Transverse & longitudinal waves

State what is meant by a transverse wave.

Figure 2 shows apparatus that is used to investigate stationary waves on a stretched wire.

A block of weight W is used to keep the wire under tension.

The frequency of the ac supply is varied until a stationary wave is produced on the wire.

Explain how a stationary wave is produced on the wire.

Figure 3 shows a small section of the wire at one instant. Five points on the wire are labelled P₁ to P₅. The dashed line represents the position of the wire when the ac supply is turned off.

Describe how the phase of the oscillating particles varies along the wire

A student investigates stationary waves on a wire using the apparatus in Figure 2. The investigation requires the student to produce the first five harmonics on the wire.

The student needs to choose one of two wires, A or B, for the investigation.

The mass of a 2.00 m length of wire A is 1.32 g. The mass of a 2.00 m length of wire B is 2.94 g.

The ac supply can produce signals in the range 1 Hz to 50 Hz. The length of the wire that vibrates between the vibration generator and the pulley is 1.50 m.

The student needs to choose one value for weight W for the investigation. W can be either 1.0 N or 5.0 N.

Determine, in kg m⁻¹, the mass per unit length of each wire. Go on to suggest which wire and which value of W the student should use to produce the first five harmonics.

A detector measures the intensity of light from a source S₁. Polaroid material is placed between source S₁ and the detector. When the material is rotated through a small angle, the detected intensity does not change. When this procedure is repeated for a source S₂, the detected intensity decreases.

A longitudinal wave of frequency 660 Hz travels through a medium.

Which statement describes the motion of a particle in the wave?

Figure 1 shows apparatus used to investigate the properties of microwaves. The microwaves from the transmitter T are vertically polarised and have a wavelength of about 3 cm. The microwaves are detected at the receiver by a vertical metal rod R.

Explain how the apparatus can be used to demonstrate that the waves from T are vertically polarised.

Figures 2a and 2b show T and R and two different positions of a metal plate M that reflects microwaves. M is vertical and parallel to the direct transmission from T to R.

In an experiment, T and R are about two metres apart. M is moved slowly towards X Figure 2a shows the initial position of M. Figure 2b shows M when it has been moved a few centimetres.

The arrowed lines show the path of waves that reach R directly and the path of waves that reach R by reflection from M.

Explain what happens to the signal detected by R as M is moved slowly towards X.

Figure 3 shows an arrangement used in a different experiment to try to determine the wavelength of the microwaves.

A double-slit arrangement is placed between T and R.

The initial position of R is the same distance from each slit and is 0.45 m from the midpoint of the two slits. AB is a line perpendicular to the line between T and the initial position of R. R can be moved 0.25 m towards A and 0.25 m towards B along AB.

The two slits act as two coherent sources with a separation of 0.12 m.

Suggest why Young’s double-slit equation should not be used to determine the wavelength.

The wavelength is known to be about 3 cm.

Deduce whether this practical arrangement is suitable for a determination of a value for the wavelength.

Unpolarised light travels through two polarising filters X and Y and is then incident on a screen. When X and Y are arranged as shown, there is a maximum intensity on the screen. X is held stationary but Y is rotated in a plane at right angles to the beam so that θ increases.

What are the next three values of θ, in rad, for which the beam hits the screen with maximum intensity?

A loudspeaker cone is driven by a signal generator (oscillator). Figure 8 shows the variation of displacement with time t for a point P at the centre of the cone. P is oscillating with simple harmonic motion.

State the time, in milliseconds, when P is moving at its maximum positive velocity.

Calculate the maximum acceleration of P.

The loudspeaker creates variations in pressure and produces a sound wave in the air around it.

State the type of wave produced and describe the motion of the particles in this type of wave.