Light

• what is light?

  Light is a form of energy that travels by electromagnetic waves
• What is reflection of light?

  the way in which light 'bounces' off surfaces
• What is Diffuse Reflection?

  the way in which light is reflected off an object that one would not normally regard as reflective.
• what is Regular Reflection?

  the way light reflects off smooth surfaces like mirrors
• what is an incident ray?

  the ray of light falling onto the mirror
• what is a normal?

  a normal, at the point of incidence, is an imaginary line radiating perpendicularly from the mirror at the point where the incident ray strikes the mirror
• what is a reflected ray?

  the ray of light bouncing off the mirror
• angle of incidence?

  the angle between the normal and incident ray
• angle of reflection?

  the angle between the normal and reflected ray
• what is an object (in optics)?

  the source of light directly prior to striking the mirror
• what is an image (in optics)?

  the location from which the rays of light appear to be coming
• object distance (u)?

  the distance between mirror and object
• image distance (v)?

  the distance between mirror and image
• what is parallax?

  the relative movement of two objects due to the movement of the observer.
• when is an image magnified?

  if its height is greater than that of the object
• when is an image diminished?

  if its height is less than that of the object
• when is an image inverted?

  when it is upside down
• when is an image erect?

  when it is the same side up
• when is an image laterally inverted?

  when the right side of the object is on the left side of the image and vice versa
• what is a real image?

  an actual intersection of light rays
• what is a virtual image?

  the apparent intersection of light rays
• what is the pole of a spherical mirror?

  its centre point
• what is the centre of curvature of a mirror?

  the centre of the sphere from which the mirror is made
• what is the principal axis of a spherical mirror?

  the straight line joining the pole to the centre of curvature
• what is the focus or focal point?

  the point halfway between the centre of curvature and the pole
• what is the focal length?

  the distance from the focus to the pole
• what is Refraction of light?

  the way in which light 'bends' when it passes from one medium to another
• what is the refractive index of a medium?

  the ratio os sine i to sine r when the light travels from a vacuum to that medium
• what is Total Internal Refection (TIR)?

  the optical phenomenon where light is reflected back from a boundary between two media. Occurs when light travelling from rarer medium to denser medium strikes the normal at an angle > Critical angle
• what is the Critical Angle?

  the angle of incidence in the denser medium which causes an angle of refraction of 90º
• what is the optic centre?

  the centre point of the lens
• what is the principal axis of a lens?

  the straight line passing through the optic centre that enters the lens at right angles to the face of the lens
• what is the principal focus (or focus) of a lens?

  the point through which light travelling parallel to the principal axis converges to for a convex lens or appears to diverge from a concave lens
• what is the focal length of a lens?

  the distance from the focus to the optic centre
• what is the Power of a lens?

  the inverse of the focal length
• what are Compound lenses?


  combinations of two or more lenses in contact with eachother
• what is Accommodation?

  the process of adjusting the focal length of the lens to focus distant or near objects clearly on the retina
• what does short-sightedness mean?


  distant objects cannot be seen clearly
• what does long-sightedness mean?


  near objects cannot be seen clearly
• what is the Spectrum?

  the range of wavelengths present in the electromagnetic radiation