specular reflection
rays are reflected from a smooth surface; they are reflected so that a clear image is formed, reflected rays are parallel
diffuse reflection
when rays are reflected from a rough surface, they are reflected in many directions and no clear image is formed, parallel incident rays get reflected at random angles
the law of reflection
the incident ray, the reflected ray and the normal to the surface all lie in the same plane, and the angle of the incidence equals the angle of reflection
virtual image
if the light energy doesn’t flow from the image
concave mirror
has a surface that is curved inwards - concentrates light rays
convex mirror
has a surface that is curved outward - spreads out light
focal point
half the centre (radius) of curvature
refraction
when light passes from one medium to another its direction changes
dispersion
the change in refractive index with wavelength
refractive index
for any substance as the wavelength of light increases, the refractive index decreases
converging/convex lens
thicker at the center than at the edges
diverging/concave lens
thinner at the center than at the edges
diffraction
how waves spread out when they pass through an opening or around an obstacle, instead of traveling in straight lines as predicted by simple ray (geometric) optics.
magnification
ratio of the size of the image formed by an optical system to the size of the object.
real image
an image formed when light rays actually meet (converge) at a point after reflection or refraction.
