p12 flashcards

What is a wave?

A wave transfers energy from one place to another and can also carry information. All waves involve oscillations which allow energy to be transferred without particles moving from one place to another.

·       What is the difference between mechanical and electromagnetic waves?

Mechanical waves involve particle oscillations (e.g. sound, water), while electromagnetic waves involve oscillations in the electromagnetic field and do not require particles (e.g. light, radio).

·       What are transverse waves?

Transverse waves have oscillations that are perpendicular to the direction of energy transfer.

·       What are longitudinal waves?

Longitudinal waves have oscillations that are parallel to the direction of energy transfer and include areas of compression and rarefaction.

·       In a wave, do particles travel with the wave?

 No, particles oscillate around a fixed point. The energy is transferred by the wave, not by the movement of particles themselves.

·       What is amplitude?

The maximum displacement of a point on the wave from its undisturbed position.

·       What is wavelength (λ)?

The distance between equivalent points on consecutive waves (e.g., peak to peak in transverse, compression to compression in longitudinal).

·       What is frequency (f)?

The number of complete waves that pass a point per second. Measured in hertz (Hz).

·       What is the period (T) of a wave?

The time it takes to complete one full wave. T = 1 / f

·       What is wave speed (v) and its equation?

The speed at which the wave travels through a medium. Equation: v = f × λ

·       How do you measure wave speed in a ripple tank?

1. Measure several wavelengths and divide by number of waves.
2. Count number of waves passing a point in 10 seconds (then divide by 10 for frequency).
3. Use wave speed = frequency × wavelength

·       How do you measure wave speed in a solid string?

1. Set up a vibration generator with a string under tension.
2. Observe stationary waves.
3. Measure the length of multiple half-wavelengths and double the average to get the full wavelength.
4. Use the known frequency and calculate wave speed using v = fλ

·       What is ultrasound and what are its uses?

Ultrasound refers to sound waves with frequencies above 20 kHz.
Uses: Scanning foetuses, detecting cracks, sonar for fish or seabeds. It reflects at boundaries between media, allowing distance calculations using s = v × t

·       What are seismic waves and what do they tell us about Earth?

 P-waves: Longitudinal

- S-waves: Transverse

They provide evidence of Earth's internal structure, like the liquid outer core

·       What type of wave is a sound wave and what does it require?

A longitudinal wave that requires a medium (solid, liquid, or gas) to travel.

How do we hear sound?

Sound vibrations travel through air into the ear, causing the eardrum to vibrate. These vibrations are passed to the inner ear, then converted to electrical impulses that go to the brain.

What is the human auditory range?

20 Hz to 20,000 Hz. Sounds above this range are called ultrasound.

How does the existence of shadow zones show there is a liquid outer core?

P-waves are refracted at the boundary between the mantle and the outer core when the waves enter the core and leave the core. Because the second refraction is further around the waves can’t reach the shadow zone

2)weak p waves detected in the shadow zone

How does the amplitude affect the energy carried by the wave

The bigger the amplitude of the waves the more energy they carry

What is meant by the reflection of waves?

Reflection occurs when waves strike a surface or boundary and are bounced back. Plane waves hitting a straight barrier are reflected at the same angle as the incident waves (angle of incidence = angle of reflection).

What does a ripple tank show when investigating reflection?

A ripple tank shows the wavefronts moving towards a barrier and being reflected. Straight wavefronts hitting a barrier at an angle reflect at the same angle.

How does the angle of incidence compare to the angle of reflection?

They are always equal — this is known as the law of reflection.

What is refraction and when does it occur?

Refraction is the change in direction of waves when they cross a boundary between two different materials at an angle, caused by a change in speed.

How do water waves behave when moving from deep water to shallow water?

The waves slow down and bend towards the normal because the shallow water makes them travel more slowly.

How does wave direction change at a boundary if the wave hits it at 90°

The wave will change speed but not direction.

What happens to frequency and wavelength during refraction?

Frequency stays the same, but wavelength changes due to change in speed.

What does the term "transmitted" mean in wave behavior at boundaries?

It means the wave passes through the new material, although speed and direction may change.

How do materials affect wave transmission, reflection, and absorption?

Some materials reflect waves, some absorb them (reducing amplitude), and some allow partial or full transmission depending on their properties.

What is a pure note, and how can it be shown on an oscilloscope?

A pure note is a smooth, regular waveform with one frequency. On an oscilloscope, it appears as a sine wave.

What is echo sounding and how is it used?

It uses high-frequency sound waves to measure depth underwater by timing how long it takes for the echo to return.

What is the formula for echo sounding depth calculations?

Depth = (speed of sound in water × time) ÷ 2

What does seismic evidence suggest about Earth's structure?

Earth has a solid inner core, liquid outer core, a mantle, and a crust, with the outer core causing S-wave blockage.