Topic 4 - Waves Flashcards
(26 cards)
How do waves transfer energy and information
Waves transfer energy and information without transferring matter
What is the frequency of a wave
The number of waves that pass a given point each second
What is the wavelength of a wave
The distance from a point on a wave to the same position on the adjacent wave
What is the amplitude of a wave
The maximum displacement on the wave from its undistributed position (midpoint to peak/trough)
What is the period of a wave
The length of time it takes for one full wave to pass through a point
What is wave velocity
The product of wavelength and frequency of the wave (measured in m/s)
What is a longitudinal wave
A wave for which the oscillations are parallel to the direction of energy transfer
What is a transverse wave
A wave for which the oscillations are perpendicular to the direction of energy transfer
What are examples of longitudinal waves
- Sound waves
- Seismic p-waves
What are the equations for wave speed
Wave speed (m/s) = frequency (Hz) x wavelength (m)
Wave speed (m/s) = distance (m) / time (s)
How do you measure the velocity of sound in air
Place a person a known distance away from a source of sound, create a sound and measure time it takes for the person to hear the sound. Do distance/time to work out wave velocity
How do you measure the ripples on water surfaces
- Set up the ripple tank with about 5 cm depth of water.
- Adjust height of wooden rod so it just touches the surface of the water.
- Switch on lamp and motor and adjust until low frequency waves can be clearly observed.
- Measure length of a number of waves then divide by the number of waves to record wavelength.
- Count number of waves passing a point in ten seconds then divide by ten to record frequency.
- Calculate the speed of the waves using: wave speed = frequency × wavelength.
What is reflection in waves
When a wave bounces of a surface
What is refraction?
The change in speed of a wave as it reaches a boundary between two mediums usually resulting in change of direction if enters at an angle
What occurs when light is refracted at a boundary
- The light changes speed and direction in the new medium
- If the new medium is more dense, the light will travel slower and bend towards the normal
- If the new medium is less dense, the light will travel faster and bend away from the normal
What is the normal in terms of reflection and refraction
A vertical imaginary line which is perpendicular to the boundary
What does it mean if a wave is transmitted
It is passed across or through a medium or substance
What is absorption
When a wave’s energy is transferred to the material it interacts with and the internal energy of the material will increase
Fill in the gap: Different substances may reflect, refract, transmit or absorb waves that vary with ___________
Different substances may reflect, refract, transmit or absorb waves that vary with wavelength
How do sound waves travel through a solid
The particles in the solid vibrate and transfer kinetic energy through the material
How does the human ear work?
- Outer ear collects sound which travels into ear
- Sound waves cause eardrum to vibrate at same frequency
- This is amplified by three ossicles (small bones)
- This causes hair in the cochlea to vibrate
- Cochlea converts vibration into electrical signals
- Signals passed to brain through auditory nerve
- Brain converts electrical signals into sound
What is human hearing range?
20-20000 Hz
What is an ultrasound wave
Sound wave with frequency over 20,000 Hz
What is an infrasound wave
A sound wave with frequency less than 20 Hz
