Science
How are shadows made?
Quick answer
A shadow is a dark area made when an opaque object blocks light. Because light travels in straight lines, it cannot bend round the object, leaving a dark shape behind it.
In one sentence
A shadow is the dark shape made when an object blocks light. Light travels in straight lines and can't bend around the object, so the space behind it stays dark.
Explained
Light travels in straight lines. When an opaque object, one that doesn't let light through, gets in the way, the space behind it gets no light. That dark patch is a shadow.
Think of a garden hose spraying a wall: hold your hand in the spray and the wall behind it stays dry. Light works the same way.
What you need
- a light source, such as the Sun, a lamp or a flashlight (a torch in the UK)
- an object that blocks light
- a surface for the shadow to fall on, such as the ground or a wall
Dark, faint or no shadow?
It depends on the material:
| Material | Lets light through? | Shadow | Examples |
|---|---|---|---|
| opaque | no | dark and clear | wood, cardboard |
| translucent | some | faint | tissue paper, frosted glass |
| transparent | almost all | hardly any | clear glass |
Changing a shadow's size
- Move an object closer to the light and its shadow gets bigger.
- Move it farther from the light (closer to the wall) and the shadow gets smaller and sharper.
Shadows outdoors
The Sun seems to move across the sky because Earth spins (see day and night). In the morning and evening, when the Sun is low, shadows are long. Around midday, when the Sun is highest, they are short. A shadow always points away from the Sun. Midday shadows also change with the seasons: they are shortest in summer.
Examples
Worked example: in the morning the Sun is low in the east, so your shadow is long and points west. At lunchtime it is short. By late afternoon the Sun is low in the west, so your shadow is long again and points east.
- Shadow puppets on a bedroom wall.
- A tree's shade keeping you cool in summer.
- A sundial's pointer casting a shadow that moves around the dial.
sun
tree
lamp
hand
Common mistakes
- "A shadow is a reflection." A reflection is light bouncing back. A shadow is where light is missing.
- "Shadows show colors and faces." A shadow is just a dark outline. It doesn't show details or the color of the object.
- "The Sun really moves across the sky." It looks that way because Earth is spinning.
Quick quiz
Shadows
Check what you know with 4 quick questions.
Question 1 of 4
What do you need to make a shadow?
Practise it
Try it
- Why does cardboard make a darker shadow than tissue paper?
- You move a toy closer to a flashlight. What happens to its shadow?
- When is your shadow longest: 8 a.m., noon or 1 p.m.?
Answers: 1) Cardboard is opaque and blocks all the light; tissue paper is translucent and lets some through. 2) It gets bigger. 3) 8 a.m., when the Sun is low.
Light and shadow activities
Practise it step by step in a full course: Grade 3 Science
For grown-ups
Related topics
Light
Light is a form of energy that travels in straight lines, very fast. We see things when light from them enters our eyes, either because they make light or because they reflect it.
Seasons
Seasons happen because Earth is tilted. As Earth orbits the Sun over a year, each half of the planet takes turns leaning towards the Sun, getting more direct sunlight and longer days.
The solar system
The solar system is the Sun and everything that orbits it, including eight planets, their moons, dwarf planets such as Pluto, asteroids and comets.
Solar and lunar eclipses
An eclipse happens when the Sun, Earth and Moon line up. In a solar eclipse the Moon blocks the Sun; in a lunar eclipse Earth's shadow falls on the Moon.
The Moon
The Moon is Earth's natural satellite, a rocky ball about a quarter of Earth's width that orbits us roughly once a month. It shines by reflecting sunlight.
Electric circuits
An electric circuit is a complete loop that electricity flows around. A simple circuit has a battery, wires and a component like a bulb. If the loop is broken, the electricity stops.