Module 4.3 – Light: Reflection, Refraction & Lenses

24 vocabulary flashcards covering key reflection, refraction, and lens terminology from the Module 4.3 review notes.

Luminous

An object that produces and emits its own light, e.g., the Sun or a light bulb.

Refractive Index

A measure of how much light slows down and bends when entering a material; higher values mean greater bending.

Total Internal Reflection

The complete reflection of light back into a medium when it strikes the boundary at an angle greater than the critical angle.

Concave Lens

A lens that curves inward at the centre and spreads parallel rays outward, always forming upright, diminished, virtual images.

Convex Lens

A lens that bulges outward at the centre and converges parallel rays, producing real or virtual images depending on object distance.

Incident Ray

The beam of light that approaches and strikes a surface or boundary.

Reflected Ray

The beam of light that bounces off a reflective surface, leaving at an angle equal to the angle of incidence.

Normal (Optics)

An imaginary line drawn at 90° to a surface where light strikes or exits; angles of incidence and refraction are measured from it.

Angle of Incidence

The angle between the incident ray and the normal at the point of contact with a surface.

Angle of Reflection

The angle between the reflected ray and the normal; equal to the angle of incidence for a plane mirror.

Refraction

The bending of light as it passes from one medium into another with a different refractive index.

Critical Angle

The minimum angle of incidence inside a denser medium that results in a 90° refracted ray along the boundary.

Plane Mirror

A flat mirror that produces upright, laterally inverted, virtual images the same size as the object and located behind the mirror.

Real Image

An image formed when light rays actually converge; it can be projected onto a screen.

Virtual Image

An image formed when light rays only appear to diverge from a point; cannot be projected onto a screen.

Focus (Focal Point)

The point at which converging light rays meet (or appear to meet) after passing through a lens or reflecting from a mirror.

Lateral Inversion

The left–right reversal of an image seen in a plane mirror.

Specular Reflection

Reflection from a smooth surface that preserves image clarity, producing sharp images.

Diffuse Reflection

Scattering of light from a rough surface, causing no clear image to form.

Speed of Light in a Medium

The rate at which light travels through a substance; slower in higher–index media like glass or water compared with air.

Bending Towards the Normal

The direction light takes when entering a medium of higher refractive index (slower speed).

Bending Away from the Normal

The direction light takes when entering a medium of lower refractive index (faster speed).

Diminished Image

An image that is smaller than the object, often produced by concave lenses or by convex lenses when the object is beyond 2F.

Science4fun Coin Disappearance

A demonstration of refraction causing a coin to reappear as water alters the light path to the observer's eye.