Physics Waves 2 Definitions Flashcards
Refraction
Change of direction of a wave as it changes speed when crossing a boundary between 2 media. Most often the wave is light.
Ray
A distinct, narrow path of light showing the direction of travel of the light waves.
Angle of Incidence
The angle of an incident light ray to the normal.
Angle of Refraction
The angle of a refracted light ray to the normal.
Total Internal Reflection
When going from more to less dense, light will be totally internally reflected at a boundary if the angle of incidence is greater than the critical angle. The angle of reflection will be the same as the angle of incidence.
Critical Angle
The largest angle of incidence possible where refraction along the boundary occurs. Angle of refraction equals 90 degrees. Beyond the critical angle, total internal reflection occurs.
Converging Lens
A lens that makes light rays converge towards the principal axis - often forming a real image.
Diverging Lens
A lens that makes light rays diverge away from the principal axis - always forms a virtual image.
Focal Length f
The distance between a lens and the point where parallel rays (from infinity) are brought together to a focus. Or for a diverging lens, the distance between the lens and the point where diverged parallel rays appear to come from.
Focal Point
The point at which rays or waves meet after reflection or refraction, or the point from which diverging rays or waves appear to emanate from. May or may not be at the focal length.
Principal Axis
The axis through the centre of a lens, perpendicular to the plane of the lens.
Real Image
An image formed when multiple rays meet and coincide, passing through a single point. It will be formed on a screen.
Virtual Image
An image we see, depicting where rays appear to come from. No rays pass through a single point. It cannot be viewed on a screen.
Diffraction
Spreading out of waves through a gap or around an object (into shadow regions). More noticeable when the wave is similar in size to the gap or obstacle.
Huygens’ Construction
All points on a wavefront act as secondary sources of waves, or wavelets, themselves. A new wavefront may be determined by considering the superposition of multiple wavelets from multiple points on a wavefront.
Plane Polarisation
Occurs with electromagnetic waves, when their plane of oscillation is constrained into a single plane. Only occurs for transverse waves and not possible for longitudinal waves.
Polarising Filter
Converts unpolarised electromagnetic radiation to be polarised.
