p6 Flashcards
what is a wave?
a wave is a disturbance that transfers energy without transferring matter
what is an oscillation?
object repeatedly moving back and forth in a regular rhythm
what are transverse waves?
oscillations are perpendicular to the direction of energy transfer (or the direction of wave travel)
what are longitudinal waves?
oscillations are parallel to the direction of energy transfer (or wave travel)
what is the wavelength of a wave?
the distance from one point on a wave to the corresponding point on an adjacent wave
what is amplitude of a wave?
the maximum displacement of a point on a wave from the resting position
what is the frequency of a wave?
the number of waves passing a point in one second. measured in Hz
what is the time period of a wave?
time for one wave to pass a point. measured in seconds (s)
what is the equation that links frequency and time period
time period = 1/ frequency
what is the equation that links frequency, wavelength and wave speed
wave speed = frequency * wavelength
what four things can happen to a wave when it meets a boundary?
- absorption
- reflection
- transmission
- refraction
what is reflection
occurs when a wave or particle bounces from the surface of an object or from the boundary between two materials
what is the normal in waves?
an imaginary line 90° to the surface/ boundary and acts at the point of interaction
what is the law of reflection?
the angle of incidence is equal to the angle of reflection (only for specular reflection)
what is refraction?
refraction is the change in the direction of a wave as it passes from one material into another across a boundary due to a change in wave speed
what happens when a wave travels from a less dense to a more dense medium? e.g from air to glass
TAG - towards air glass
wave refracts towards the normal
what happens when a wave travels from a more dense medium into a less dense medium? e.g from glass to air
AGA - away glass air
the wave refracts away from the normal
what is a lens?
a lens is a transparent block that has been shaped to retract light to form an image
what is the principle focus of a lens?
the point at which the light rays meet
what is the focal length of a lens?
the distance between the centre of a lens and the principal focus
what are the three steps for constructing lens ray diagrams?
- draw a ray parallel to the principal axis from the top of the object to the lens
- continue from the end of the parallel ray, drawing a ray that passes through the principal focus
- draw a ray from the top of the object through the centre of the lens
what are the three ways to describe images formed by lenses?
- upright or inverted
- magnified or diminished
- real or virtual
what are five properties or EM waves?
- all transverse waves
- travel at the speed of light (3x10^8)
- can travel through a vacuum
- follow the wave speed equation
- can be reflected or refracted
state the types of wave in order of decreasing wavelength
radio
micro wave
infrared
visible
ultraviolet
x ray
gamma ray