physics test waves Flashcards
amplitude
– the distance from the equilibrium position to the maximum displacement
wavelength
the distance between a point on one wave and the corresponding point on the next wave
Frequency
the number of waves that pass a single point per second
Speed
the distance travelled by a wave each second
what is speed related to
frequency and wavelength
What does speed equal
𝒇𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚 × 𝒘𝒂𝒗𝒆𝒍𝒆𝒏𝒈𝒕𝒉
transverse waves
Has crests and troughs
Vibrations of the particle are at right angles to the direction
of travel of the wave
An example is light
Longitudinal waves
Consists of compressions (particles pushed together) and rarefactions
(particles moved apart)
Vibrations of particles are parallel to the direction of travel
of the wave
An example is sound
what is a wavefront
a surface containing points affected in the same way by a wave at a given time such as crests or troughs.
Reflection
Waves reflect off smooth, plane surfaces rather than
getting absorbed
Angle of incidence = angle of reflection
Rough surfaces scatter the light in all directions, so they
appear matte and unreflective
Frequency, wavelength, and speed are all unchanged
Refraction
The speed of a wave changes when it enters a new medium
If the wave enters a more optically dense medium, its speed
decreases and it bends towards the normal
If the wave enters a less optically dense medium, its speed
increases and it bends away from the normal
In all cases, the frequency stays the same but the wavelength
changes.: speed is proportional to wavelength.
diffraction
Waves spread out when they go around the sides of
an obstacle or through a gap
The narrower the gap or the greater the
wavelength, the more the diffraction
Frequency, wavelength, and speed are all unchanged
What happens when light is reflected of a plane mirror
Upright Same distance from the mirror as the object Same size Virtual A line joining object and image cuts the mirror at right angles.
when can refraction be shown
when light is passed through a glass slab at an angle to its normal
When light enters a more optically dense medium
the angle of incidence is greater than the angle of refraction
The opposite is true when light enters a less optically dense medium.
Angle of incidence
The angle between the incident ray
and the normal
angle of refraction
The angle between the refracted ray and the normal
The refractive index n of a medium is defined as
the ratio between the speed of light
Total internal reflection occurs when
the angle of incidence is greater than the critical angle and the light reflects back into the medium.
the light must also be travelling from a more optically dense medium into a less
optically dense medium (most common example is glass to air).
optical fibre
a long thin rod of glass surrounded by cladding which uses total internal reflection to transfer information by light, even when bent.
converging (convex) lens
A transparent block which brings light rays together at a point
called the principal focus by utilising refraction.
focal length
the distance between the centre of the lens and the principal focus.
when are real images formed
when the distance of the object from the centre of the
lens is greater than the focal length. They are images where light actually
converges to a position and can be projected onto a screen.
When are virtual images formed
When the distance of the object from the centre of
the lens is smaller than the focal length. They are images where light only
appears to have converged and they cannot be projected onto a screen.
