The statement below is followed by four options. Each option is related to the item in the statement, but only one is always true. Select the option that always holds and makes the statement true.
"A shadow always needs ______."
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A source of light
The answer must hold for every shadow, without exception. An option that is present in most cases but can be missing in even one case is not always true.
Option (1) Sunlight — a torch, a candle or a bulb also casts shadows.
Option (2) A white screen — a surface is needed to catch the shadow, but it can be the ground, a wall or any surface, of any colour.
Option (3) A source of light — a shadow forms only when an object blocks light coming from a source; with no light there is no shadow, so this is always true.
Option (4) A transparent object — a transparent object lets light pass and gives no clear shadow; a shadow needs an opaque object.