# Light Waves

In this worksheet, students will be introduced to light as waves, which will be compared to waves in matter.

Key stage:  KS 3

Curriculum topic:   Physics: Waves

Curriculum subtopic:   Light Waves

Difficulty level:

### QUESTION 1 of 10

Light is all around us and we can see objects because of it. Light is created by luminous objects like the Sun. We can see everything, because light bounces off objects around us and enters our eyes.

Light is a wave and travels in straight lines, as shown by this laser beam in the picture.

Shadows are formed because light cannot travel through some objects and cannot bend around them either.

Light is part of a group of waves called the Electromagnetic Spectrum (see diagram).

Not all waves on the Electromagnetic Spectrum are visible to us: visible light is made of various colours that altogether make up white light. The diagram below shows white light dispersed into its different colours by a prism:

Light travels at 300 000 km/s. It takes light 8.5 minutes to reach the Earth from the Sun.

Apart from the electromagnetic waves, there are also matter waves, like water waves and sound waves. These travel at a much lower speed. Whereas light can travel in a vacuum, i.e. a place with no particles (like empty space), matter waves need a medium, i.e. particles, to travel in. That's how light can travel in space, but sound cannot. Additionally, matter waves are not emitted by particles, but just travel in them and they have much smaller wavelengths. To understand what wavelength is, study the diagram below, which shows the wavelengths of all visible light colours, which themselves travel at different wavelengths.

What objects give out light?

dark

bright

luminous

How can we see objects around us?

Light reflects off them and scatters around.

Light bends off objects and enters our eyes.

Light bounces off objects and enters our eyes.

Is this statement true or false?

Light bends around objects as it travels.

true

false

What is formed when light cannot travel through some objects?

rainbow

bright colours

Light is part of which group of waves?

The Electrophoretic Spectrum

The Electromagnetic Spectrum

The Electromagnet Spectrum

Is this statement true or false?

White light is made of various other colours.

true

false

What is the speed of light?

300 000 km/s

300 000 000 km/s

300 000 m/s

How long does it take for light from the Sun to reach the Earth?

8.5 seconds

8.5 minutes

8.5 hours

Is this statement true or false?

Light waves travel more slowly than waves in matter.

true

false

Apart from speed, tick three other differences between light waves and waves in matter.

Light waves can travel in a vacuum.

Light waves have much smaller wavelengths.

Light waves have longer wavelengths.

Waves in matter only travel in particles and are not emitted by them.

Waves in matter can travel in a vacuum.

• Question 1

What objects give out light?

luminous
EDDIE SAYS
Objects that give out light are called luminous objects.
• Question 2

How can we see objects around us?

Light bounces off objects and enters our eyes.
EDDIE SAYS
We can see, because light bounces off objects and enters our eyes. Option 3 is correct. Option 1 uses the correct scientific term 'reflects', but does not mention light entering the eyes. Option 2 mentions light 'bending off', which is not correct scientifically.
• Question 3

Is this statement true or false?

Light bends around objects as it travels.

false
EDDIE SAYS
The statement is false. Light only travels in straight lines.
• Question 4

What is formed when light cannot travel through some objects?

EDDIE SAYS
Light cannot travel through some objects, so shadows are formed.
• Question 5

Light is part of which group of waves?

The Electromagnetic Spectrum
EDDIE SAYS
Light is part of a group of waves called the Electromagnetic Spectrum.
• Question 6

Is this statement true or false?

White light is made of various other colours.

true
EDDIE SAYS
The statement is true; white light is made of seven other colours.
• Question 7

What is the speed of light?

300 000 km/s
EDDIE SAYS
The speed of light is 300 000 km/s.
• Question 8

How long does it take for light from the Sun to reach the Earth?

8.5 minutes
EDDIE SAYS
It takes light from the Sun 8.5 minutes to reach the Earth.
• Question 9

Is this statement true or false?

Light waves travel more slowly than waves in matter.

false
EDDIE SAYS
The statement is false. Light waves travel much faster than waves in matter.
• Question 10

Apart from speed, tick three other differences between light waves and waves in matter.

Light waves can travel in a vacuum.
Light waves have longer wavelengths.
Waves in matter only travel in particles and are not emitted by them.
EDDIE SAYS
1) Light waves can travel in a vacuum.
2) Light waves have longer wavelengths.
3) Waves in matter only travel in particles and are not emitted by them.
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