P4 Light & Shadows (Concept Map)
Primary 4 Science — Concept Map
Created by Miss Clarissa Ng · www.clartutors.com
Light travels in straight lines
How we see things, and how a shadow forms when light is blocked
You see an object either because it is a light source or because it reflects light into your eyes.
Light travels in straight lines, which is why a blocked light leaves a shadow behind the object.
A shadow needs a light source + an object + a screen, and it follows the object's outline.
Object nearer the source or screen further away → bigger; object nearer the screen → smaller.
A low Sun in the morning or evening gives long shadows; noon gives the shortest.
Seeing things
Light sourcesan object that gives off its own light, such as the Sun or a lamp
Natural or man-madenatural: the Sun, stars, lightning; man-made: lamps and torches
Reflected lightan object that is not a light source can only be seen when light from a light source reflects off it
Moon and mirrorsthe Moon and a mirror do not give off their own light
Light travels in straight lines
A straight pathlight travels in straight lines from its source; it does not bend around objects
Blockedwhen light meets an object it cannot pass through, the light is blocked and forms a shadow
Shadows prove itthe shadow follows the outline of the object that blocked the light
What a shadow needs
Three thingsa light source, an object to block the light, and a screen for the shadow
Blocked completelyan object that blocks all the light gives a dark shadow
Blocked partlyan object that lets only some light through gives a lighter shadow
What changes a shadow
Nearer the light sourcemoving the object closer to the light source makes the shadow bigger
Nearer the screencloser to the screen makes the shadow smaller
Screen moved awaymoving the screen further away makes the shadow bigger
Shape and sizethe shadow takes the shape of the blocking object
Shadows during the day
Morningthe Sun is low in the east, so shadows are long and point west
Noonthe Sun overhead at noon gives the shortest shadow
Eveningthe Sun is low in the west, so shadows are long and point east