6.1 Waves in air, fluids and solids Flashcards
What are the types of waves? (2)
- Longitude
- Transverse
What is an example of a longitude wave? (1)
Sound waves travelling in air.
What is an example of a transverse wave? (1)
Ripples on a water surface.
What is a transverse wave? (1)
A wave in which the direction of energy transfer is perpendicular to the oscillations.
What is a longitudinal wave? (1)
A wave in which the direction of energy transfer is parallel to the oscillations.
What does a wave transfer? (2)
Energy
What is the difference between transverse and longitudinal waves? (1)
Transverse waves require a medium to travel in, whilst not all longitudinal waves require one.
What are the parts of a longitudinal wave called? (2)
- Compressions (tight areas)
- Rarefactions (loose areas)
How do you describe the evidence that the waves, and not the air or water itself travels for both ripples on a water surface and sound waves in air? (2)
Water surface: a boat bobs up and down, like the water molecules do in a localised motion, but they don’t move along with the wave.
Air: small polystyrene beads move back and forth, like air particles do in their equilibrial position, but they don’t move along with the sound wave.
What is the amplitude of a wave? (1)
The maximum displacement of a point on a wave away from its undisturbed position.
How do you measure the amplitude? (1)
Distance between crest or tough or a wave and the undisturbed point (middle of waves).
What is the wavelength of a wave? (1)
The distance from a point on one wave to the equivalent point on the adjacent wave.
How do you measure the wavelength? (2)
- Distance between one point and the same point on the next wave wave (e.g: trough, crest or middle)
- Distance between area of compression or rarefactions to the next same area.
What is the frequency? (1)
The number of waves passing a point each second
What is the unit of frequency? (1)
Hertz, Hz (waves per second).
What is the period? (1)
The time (in seconds) for one wave to pass a point.
What is the word and symbol equation for period? (2)
period (s) = 1 / frequency (Hz)
T = 1 / f
What is the wave speed? (1)
The speed at which energy is transferred (or the wave moves) through a medium.
What is the word and symbol equation for period? (2)
wave speed (m/s) = frequency (Hz) × wave length (m)
v = f × λ
Describe a method to measure the speed of sound waves in air. (5)
- Separate two people with a distance <100m (e.g. 500m)
- Person A holds cymbals whilst Person B has a stopwatch.
- Person B should start the timer when they see Person A clash the cymbal together.
- Person B stops the timer when they hear the cymbals clash.
- Calculate speed of sound waves by dividing the distance travelled by the time taken.
What are the problems and solutions with the simple method of measuring the speed of sound waves in air? (2)
- Reaction times differ → include large number of observers with timers, remove anomalies and calculate a mean.
- Small time difference between seeing and hearing → increase distance between Person A and B.
What can happen to waves at the boundary between two different materials? (3)
- Transmitted (no change occurs)
- Absorbed (may not pass through)
- Reflected
Draw or state steps to construct a ray diagram to illustrate the reflection of a wave at a surface. (4)
- Draw incident ray from object to mirror.
- Draw a normal line where object and mirror meet
- Draw an angle between incident and normal line
- Draw a reflected ray using the reflection angle.
Diagram
Draw or state steps to use a ray diagram to work out where the image will appear in the mirror. (5)
- Draw incident ray (with arrow) from object to mirror.
- Draw normal (with arrow) at right angle to the mirror surface, and reflected line.
- Repeat this anywhere.
- Extend the two reflected rays back into the mirror (dotted lines).
- Object reflected where the lines meet.
Diagram
