---
title: "Where does the sunlight go?"
subtitle: "Year 10 Earth and space · Earth's energy balance · Lesson 3"
---

# Where does the sunlight go?

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** Fresh snow reflects about 80% of the sunlight that hits it. The open ocean reflects about 6%. When sea ice melts, that difference matters for the whole planet.


:::teacher-note

**In one sentence:** Students identify the sun as Earth's energy source and explain why different surfaces absorb or reflect different proportions of sunlight (albedo) (AC9S10U04, node 1, a hinge node).

**Students should be able to say:** I can identify the sun as Earth's main energy source. I can distinguish absorbed from reflected sunlight with examples. I can explain why melting ice increases the energy absorbed.

**Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

:::


## Engage


:::keep-together

**Sunlight reaches the Earth. What happens to it?**

☐ Some is reflected straight back to space and the rest is absorbed: how much depends on the surface

☐ All of it warms the Earth

☐ It is stored in the sun's rays

☐ It all bounces off

My prediction, and why:

{{lines-3}}

:::


:::teacher-note

**What happens:** Some is reflected and the rest is absorbed. On average Earth reflects about 30%, mostly from clouds, ice and bright surfaces. Dark surfaces like oceans absorb most of what hits them.

:::


## Explore

Try it on the board in the tutorial. Was your prediction right? What was different?

{{lines-2}}

## Explain: absorbed and reflected


:::keep-together

### Reflect or absorb

**Reflects most sunlight, or absorbs most?**

Groups: Reflects most, Absorbs most

- Fresh snow: {{field-15}}
- Open ocean: {{field-15}}
- Sea ice: {{field-15}}
- Dark forest: {{field-15}}
- Thick white cloud: {{field-15}}

:::


:::teacher-note

**Answer:** Fresh snow → Reflects most; Open ocean → Absorbs most; Sea ice → Reflects most; Dark forest → Absorbs most; Thick white cloud → Reflects most

:::


:::keep-together

### Melting ice

**Arctic sea ice melts and is replaced by open ocean. What happens to the energy absorbed there?**

☐ It stays the same

☐ It decreases

☐ It increases, which warms the area and melts more ice

☐ The ocean reflects more

:::


:::teacher-note

**Answer:** It increases, which warms the area and melts more ice

:::


:::keep-together

### Light or dark

**Why does fresh snow reflect most of the sunlight that hits it, while the open ocean absorbs most?**

☐ Water is wet, so it soaks up the light

☐ Snow is cold, so it can't take in any energy

☐ Light-coloured surfaces reflect most of the light that hits them; dark surfaces absorb most of it and warm up

☐ The ocean gets more sunlight, so it absorbs more

:::


:::teacher-note

**Answer:** Light-coloured surfaces reflect most of the light that hits them; dark surfaces absorb most of it and warm up

:::


:::typical

## Elaborate: the angle of the sun


:::keep-together

**The same sunlight hits the equator nearly straight on, but the poles at a low angle. Why do the poles get less energy per square metre?**

☐ There is no sunlight at the poles

☐ The poles are farther from the sun

☐ The same beam is spread over a bigger area, and more is reflected at low angles

☐ The sun is dimmer there

:::


:::teacher-note

**Answer:** The same beam is spread over a bigger area, and more is reflected at low angles

:::

:::


:::wider

## Elaborate: land use


:::keep-together

**A city replaces grassland with dark roads and roofs. What happens to the local energy budget?**

☐ Less is absorbed

☐ The city reflects more

☐ No change

☐ More sunlight is absorbed, so the city warms: an urban heat island

:::


:::teacher-note

**Answer:** More sunlight is absorbed, so the city warms: an urban heat island

Light-coloured roofs and more trees are used to cool cities.

:::

:::


## Evaluate: look back

Write one sentence: "At first I thought… Now I think… because…"

**Revision summary**

- The **sun** is Earth's main energy source: about 340 W/m² on average at the top of the atmosphere.
- Some sunlight is **reflected** (about 30% on average: the **albedo**); the rest is **absorbed** and warms Earth.
- Bright surfaces (ice, snow, cloud) reflect most; dark ones (ocean, forest) absorb most. Melting ice means more absorbed.

## Exit ticket

:::keep-together

**Why does replacing sea ice with open ocean warm the area?**

{{lines-3}}

:::


:::teacher-note

**Answer:** Ice reflects most sunlight (about 80%); dark ocean absorbs most (reflects about 6%), so more energy is absorbed.

:::