A wave can be described as a travelling disturbance that transports energy from one point to another - Leaving Cert Physics - Question 8 - 2021

Electromagnetic waves do not need a medium for propagation. They can travel through a vacuum, unlike sound waves which require a medium.

Transverse waves are those where the disturbance is perpendicular to the direction of wave propagation. For example, in visual representations of waves on a string, the oscillation occurs up and down while the wave moves left to right. Longitudinal waves, on the other hand, have oscillations that are parallel to the direction of wave propagation. A common example is a sound wave, where air particles oscillate back and forth in the same direction as the wave travels.

To calculate the speed (v) of the radio waves, we can use the formula: $v = f \cdot \lambda$ where: f is the frequency (107 MHz = 107 x 10^6 Hz) and \lambda is the wavelength (2.804 m). Thus, $v = (107 \times 10^6 Hz) \times (2.804 m) = 3.00 \times 10^8 m/s.$

An example of the reflection of sound waves is an echo. When sound waves travel from a source to a distant surface (such as a wall or cliff) and bounce back to the listener, the sound produced is an echo. This phenomenon illustrates how sound can reflect off surfaces.

Using Snell's Law which states that $n_1 \sin(\theta_1) = n_2 \sin(\theta_2),$ we can find the refractive index (n) of the glass. Let the refractive index of air (n1) be approximately 1, the angle of incidence (θ1) = 23°, and the angle of refraction (θ2) = 15°. Rearranging gives: $n = \frac{\sin(\theta_1)}{\sin(\theta_2)} = \frac{\sin(23°)}{\sin(15°)} \approx 1.51.$

To complete the diagram, illustrate the wave fronts spreading out as they pass through the gap. Draw lines representing the wave fronts on either side of the gap diverging from the gap to show the diffraction pattern.

One method involves using two loudspeakers placed at a set distance apart. Connect them to the same audio source and ensure they are both emitting sound waves. As the waves from each speaker meet at certain points, they will interfere either constructively or destructively, depending on their phase relationship. Participants can then listen for variations in sound intensity at different positions in the room and note where louder or softer sounds occur, illustrating the principle of interference.

Polarisation refers to the orientation of vibrations in a transverse wave to a single plane. Light waves can be polarised, which restricts their oscillations to a specific direction. In a labelled diagram, show how light vibrations are constrained to a plane, while sound waves, which are longitudinal, cannot be polarised in this manner and vibrate in multiple directions.