| A | B |
|---|
| luminous | gives off light |
| umbra | the dark part of a shadow |
| penumbra | the lighter part of a shadow |
| transparent | transmits all light |
| translucent | transmits some light |
| opaque | does not transmit light |
| crest | the top of a wave |
| trough | the bottom of a wave |
| frequency | number of waves per second |
| amplitude | the height of a wave |
| wavelength | the length of a wave |
| plane mirror | a flat mirror |
| concave mirror | a mirror that curves inward |
| convex mirror | a mirror that curves outward |
| convex lens | a lens that is thicker in the middle |
| concave lens | lens that is thicker at the sides |
| refraction | bending of light rays |
| sclera | outer white coating of the eye |
| pupil | hole in the eye that lets in light |
| iris | muscle that controls the size of the pupil |
| cornea | clear window in front of the eye |
| retina | part of the eye where the image forms |
| optic nerve | carries messages to the brain from the eye |
| rods | cells in the eye that detect light and dark |
| cones | cells in the eye that detect colours |
