Year 3 Science: Light and seeing
Part of the Year 3 Science light and shadows chapter. Chapter overview · whole chapter on one page
Light and seeing
We need light in order to see things. Light from a light source, such as the Sun or a lamp, lands on objects and bounces off them. When that light enters your eyes, you see the object.
Dark is the absence of light. It means there is no light at all. In a dark room, no light enters your eyes, so you cannot see anything.
Look at the two pictures. In the first picture the lights are off, so no light enters the eyes. In the second picture the lights are on, so light from the lamp bounces off the cup and enters the eye.
The table shows what happens in three different situations.
| Situation | Does light enter your eyes? | Can you see the cup? |
|---|---|---|
| Lights on, and a cup in front of you | yes | yes |
| Lights off, and no torch is on | no | no |
| Lights off, and a torch shines on the cup | yes | yes |
Key ideas
- We need light in order to see things.
- We see an object when light from it enters our eyes.
- Dark is the absence of light: there is no light.
- In the dark, no light enters the eyes, so we cannot see.
Method. Find the right row of the table.
- Find the row. The third row says lights off, and a torch shines on the cup.third row
- Read the column. The column Does light enter your eyes? says yes for that row.yes
- Write the answer. yes
Check. The torch lets light reach the cup, and the light enters the eyes. ✓
Watch out. Read the column headed Does light enter your eyes? for the row you want.
Method. Find the second row of the table.
- Find the row. The second row says lights off, and no torch is on.second row
- Read the last column. The column Can you see the cup? says no for that row.no
- Write the answer. no
Check. No light enters the eyes, so the cup cannot be seen. ✓
Method. Think about the path of the light.
- Follow the light. Light from the lamp lands on the book.lamp to book
- Finish the path. The light bounces off the book and enters your eyes.enters your eyes
- Write the answer. Light from the lamp bounces off the book and enters your eyes.
Check. Light must enter the eyes before we can see the book. ✓
Watch out
Watch out: your eyes do not make light. We can see because light from outside the eyes enters them.
Try it at home or school (with a grown-up). Sit in a room with the curtains closed. Switch off the lights and wait one minute. Say what you can see and what you cannot. Then switch on a torch, and point it at a book, away from your face. Switch the torch off before you put it down. Never shine a torch into anyone’s eyes.
Exam tip
Grown-up tip. Ask: “Why can you see the book now? What is the light doing?” Let your child explain the path of the light, from the torch to the book and into the eyes, in their own words.
Exercise 8A Light and seeing
Method. Look at the two pictures and the labels.
- Read the labels. The picture labelled lights off has no light entering the eyes.lights off: no light
- Find the picture with light. The picture labelled lights on has light entering the eyes, so the cup can be seen.lights on
- Write the answer. lights on
Check. Light must enter the eyes before we can see the cup. ✓
Method. Think about what dark means.
- Read the definition. Dark is the absence of light, so there is no light.no light
- Write the answer. yes
Check. With no light, you cannot see. ✓
Method. Read the definition of dark.
- Read the sentence. Dark is the absence of light, which means there is no light.no
- Write the answer. no
Check. Dark is the same as having no light at all. ✓
Method. Think about the body part for seeing.
- Think about seeing. We see with our eyes, when light enters them.eyes
- Write the answer. eyes
Check. Light enters the eyes, and then we see. ✓
Method. Find the row with lights off and no torch on.
- Find the row. The second row says lights off, and no torch is on.second row
- Read the last column. The cup cannot be seen, so the answer is no.no
- Write the answer. no
Check. No light reaches the eyes in a dark room. ✓
Method. Read the key ideas in this section.
- Read the key idea. We see an object when light from it enters our eyes.eyes
- Write the answer. eyes
Check. The light must reach the eyes. ✓
Method. Think about where the light comes from.
- Think about the light. The light comes from a light source, such as the Sun or a lamp, and not from the eyes.from outside
- Write the answer. false
Check. Your eyes do not make light. ✓
Method. Find the first row of the table.
- Find the row. The first row says lights on, and a cup in front of you.first row
- Read the last column. The column Can you see the cup? says yes.yes
- Write the answer. yes
Check. Light from the lamp bounces off the cup, so it can be seen. ✓
Method. Think about where the light comes from.
- Think about the shoes. In the dark, no light reaches the shoes, so Sam cannot see them.no light
- Decide. Eyes do not make light, so Sam is not right.no
- Write the answer. no
Check. You need light from outside to see. ✓
Method. Think about the light from the torch.
- Think about the path. The torch lights the teddy, and the light bounces off it.bounces off
- Make the prediction. So the teddy can be seen, because the light enters the eyes.teddy seen
- Write the answer. Accept any prediction that says the teddy can be seen, because light from the torch enters the eyes.
Check. A prediction should follow from what we know about light. ✓
Method. Think about the light in the room.
- Think about the room. The room has no light in it.no light
- Give the reason. So no light can enter your eyes, and you cannot see.cannot see
- Write the answer. Accept any sentence that says no light reaches the eyes, because there is no light in the room.
Check. Dark is the absence of light. ✓