Invisible Waves Flashcards
Explain, using the particle model the processes underlying the convection (understanding) and conduction (transmission) of heat energy
Convection: transfer of heat between two bodies by currents of moving gas or fluid (eg. when hot air rises, it allows cooler air to come in and be heated)
Conduction: when heat energy is transmitted through collisions between neighbouring atoms or molecules
Identify, with the use of examples the transfer of energy by waves
- transverse waves: The medium (the material moving energy from one substance to another) swings up and down, perpendicular to the direction of energy transfer.
eg. water waves
- compression/ longitude waves: the medium swings backwards and forwards, parallel to the direction in which the energy is transferred
eg. slinky
Compare longitudinal (compression) waves and transverse waves
longitudinal waves: cause the medium to move parallel to the direction of the wave
transverse waves: cause the medium to move perpendicular to the direction of the wave
Describe, using the wave model, the features of waves including frequency, wavelength and speed
frequency: the number of waves that pass a point in a certain period of time. The lower the frequency is, the slower the wave will move, and the higher the frequency, the faster the wave will move. (measured in Hz)
wavelength: distance between identical points in a transverse wave
speed: the distance the wave travels in a given amount of time eg. (m/s)
Explain, using the particle model, the transmission of sound in different media
air: in air, sound travels as a longitude wave
water: in water, sound also travels as a longitudinal wave, but the speed of sound is much faster than in air
solid materials: in solid materials, sound can travel as both longitude and transverse waves depending on the type of material and the direction of the wave
Describe how the ear functions to provide hearing
The main function of the ear is to detect sound. It collects the energy of vibrating air and changes it into electrical signals, which are sent to the brain.
Identify visible light as a form of electromagnetic radiation
Visible light is a form of electromagnetic radiation because it is a changing electric field that creates a changing magnetic field.
Identify the properties of electromagnetic waves
- transverse waves
- able to travel through most substances including through a vacuum
- speed in the air is about 300 000 km/s.
Describe the reflection of light from a plane and curved mirrors and identify some useful applications
plane mirrors: when the light rays get stroked on the flat mirror, they get reflected back
curved mirrors: light-reflecting
from concave and convex mirrors also follow the law of reflection, such that the parallel rays of light are reflected at a focal point
Describe and account for the refraction of light and outline everyday instances in which refraction is evident
Light normally travels in straight lines. However, under certain conditions, it is possible to change the direction of light. Light can be made to bend by passing it through different transparent media
eg. a stem of a flower may not look straight, this is because as light travels from water to air, it changes direction.
Describe the way in which lenses focus light and identify some useful applications of lenses
The bending of light through transparent materials can be used to produce some effects. Lenses are useful because they bend light in a predictable way and can change the
way we see the world. The type of
image produced by a lens depends
on the shape of the lens.
Describe how the eye functions to provide vision
When light hits the retina, photoreceptors turn light into electrical signals, these travel from the retina through the optic nerve to the brain.
Account for the colour of objects in terms of absorption, transmission and reflection of the colour spectrum
absorption: coloured objects can
separate white light by absorbing some colours and reflecting others. The colour of an object depends on which parts of
the spectrum are reflected towards your eyes.
When white light falls on any opaque surface, red is reflected green and blue are absorbed. Transparent objects, such as cellophane and coloured glass, split white light by absorbing some colours and allowing others to pass through.
transmission:
Identify the features of different types of radiation in the electromagnetic spectrum and their uses
ultra-voilent radiation:
- visible to the human eye
- more energetic than visible light and as a result can cause chemical changes in many
substances, including human skin
Infra-red radiation:
- visible to the human eye
- emitted by all objects, unless
those objects are extremely cold
radio waves:
- low in energy intensity
- include the electromagnetic
waves used in TV, AM and FM
radio transmissions, microwave
waves used in radar, wireless
Internet and mobile phone
communication
visible light:
- represents only a very small
part of the electromagnetic spectrum
- contains all the colours of the rainbow
Describe advances in the technology involved in our communication network, in particular, the coaxial cable, wireless and optic fibre technology
coaxial cables:
- improves the speed of communication
- transmits more calls and signals than copper cables
wireless technology:
- can carry many signals at a time, but repeater stations need to be used so the signal doesn’t fade away before reaching its destination
optic fibres:
- provides broadband speeds that will be 100x faster than those currently available
- transmits many more messages at a time
