Light as a Wave

Light as a Wave

Middle School

​

Learning Objectives

• Describe the basic properties of waves, like amplitude, wavelength, and frequency.

• Explain the arrangement of the electromagnetic spectrum and the relationship between its properties.

• Describe how light waves interact with materials through absorption, reflection, and transmission.

• Analyze the real-world effects of different types of light, like photosynthesis.

Key Vocabulary

​

Wavelength

This is the distance between two consecutive peaks or troughs of a light wave.

​

Amplitude

The height of a wave from its equilibrium position, which relates to its brightness.

​

Frequency

This is the number of waves that pass a specific point in a given time.

​

Absorb

To take in light energy and convert it into another form, such as heat.

​

Reflect

To bounce light off a surface, which is how we see non-luminous objects.

​

Transmit

To allow light to pass through a material, like with a pane of glass.

Key Vocabulary

​

EM Spectrum

The entire range of light that exists, from radio waves to gamma rays.

​

Photosynthesis

The process plants use to convert light energy into chemical energy as sugars.

​

Ultraviolet (UV) Light

A type of high-energy light from the sun that can cause damage to skin cells.

​

Infrared Light

A type of light that we feel as heat, used in applications like remote controls.

​

​

What are the Properties of Waves?

• A wave is a repeating disturbance that transfers energy from one place to another.

• Wavelength is the distance from one peak of a wave to the next peak.

• Amplitude is the height of a wave, which shows the brightness of the light.

• Frequency is how many waves pass a point in a certain amount of time.

​

Multiple Choice

What is the fundamental purpose of a wave?

• It transfers energy from one place to another.

• It moves matter from one point to another.

• It creates a disturbance that stays in one place.

• It measures the distance between two points.

Multiple Choice

What is the correct way to measure the wavelength of a wave?

• The distance from one peak of a wave to the next peak.

• The number of waves that pass a point in a certain time.

• The height of a wave from its resting position.

• The speed at which the wave is traveling.

Multiple Choice

Frequency of a wave refers to:

• The distance between wave peaks

• How high the wave is

• How many waves pass a point in a given time

• The speed of the wave

​

​

The Electromagnetic Spectrum

• Light is a form of electromagnetic radiation that travels in waves.

• The spectrum is organized by wavelength, from longest to shortest.

• Shorter wavelengths have a higher frequency and more energy.

• Unlike sound, these waves can travel through the vacuum of space.

Multiple Choice

What is a key characteristic of all forms of electromagnetic radiation?

• They can all travel through the vacuum of space.

• They all have the same wavelength and energy.

• They are all visible to the human eye.

• They require a medium like air or water to travel.

Multiple Choice

What is the relationship between the wavelength and energy of an electromagnetic wave?

• As wavelength increases, energy increases.

• As wavelength decreases, energy increases.

• Wavelength and energy are not related.

• Only long wavelengths have energy.

Multiple Choice

An X-ray wave has a shorter wavelength than an infrared wave. What can be concluded from this information?

• The X-ray wave has more energy than the infrared wave.

• The infrared wave has a higher frequency than the X-ray wave.

• Both waves travel at different speeds in a vacuum.

• Only the infrared wave can travel through space.

How Light Interacts with Materials

​

Reflection

• This occurs when light bounces off an object's surface.

• Smooth surfaces like mirrors create very clear and sharp reflections.

• We see objects because they reflect light into our eyes.

​

Absorption

• This happens when a material takes in energy from light.

• A black shirt absorbs all colors of light, becoming warm.

• The light energy is converted into heat by the material.

​

Transmission

• This occurs when light passes directly through an object.

• Materials that allow light through are called transparent or translucent.

• A clear glass window is an excellent example of transmission.

Multiple Choice

Which statement best explains the process that allows us to see most objects?

• Reflection, because light bounces off the object's surface into our eyes.

• Absorption, because our eyes take in the light from the object.

• Transmission, because light passes through the object to our eyes.

• Conversion, because the object turns light into heat for us to see.

Multiple Choice

What is the key difference between how light interacts with an object through absorption versus transmission?

• Absorption converts light energy to heat, while transmission allows light to pass through a material.

• Absorption occurs in smooth materials, while transmission occurs in rough materials.

• Absorption makes objects appear clear, while transmission makes them appear dark.

• Absorption bounces light away, while transmission traps light inside an object.

Multiple Choice

If a black shirt, a mirror, and a clear glass window are left in direct sunlight, which one will become the warmest and why?

• The black shirt, because its material absorbs light energy and converts it into heat.

• The mirror, because its smooth surface reflects the most heat from the sun.

• The glass window, because it transmits light and heat equally.

• All three would be the same temperature, as they are in the same light.

Effects and Applications of Light

​

Visible Light

• ​Plants use visible light to convert CO₂ and water into food.

• ​​This vital process is commonly known by the name of photosynthesis.

• ​It is the foundation of most food chains found on Earth.

​

Infrared Light

• ​Infrared light is invisible to human eyes and is often felt as heat.

• ​​It is commonly used in TV remote controls for sending out signals.

• ​This type of light is also used in special thermal imaging cameras.

​

Ultraviolet (UV) Light

• ​UV light from the sun can damage the DNA in your skin cells.

• ​​Our atmosphere helps absorb the most dangerous and harmful of UV rays.

• ​A pigment called melanin in your skin helps absorb the UV light.

Multiple Choice

What is the primary role of visible light in the survival of plants?

• It allows them to convert CO₂ and water into food.

• It helps them absorb heat from the environment.

• It protects their cells from DNA damage.

• It is used to send signals to other plants.

Multiple Choice

How does the application of infrared light compare to the primary effect of ultraviolet (UV) light mentioned?

• Infrared light is used for signals and detecting heat, while UV light can damage skin cells.

• Infrared light is used for photosynthesis, while UV light is used in remote controls.

• Infrared light is visible as colors, while UV light is primarily felt as heat.

• Infrared light is absorbed by the atmosphere, while UV light is the basis for food chains.

Multiple Choice

A scientist is designing a satellite that needs to locate heat sources on the ground and also measure the health of forests by monitoring photosynthesis. Which two types of light must the satellite's sensors be able to detect to accomplish these tasks?

• Infrared light to detect body heat and visible light to monitor photosynthesis.

• Visible light to detect body heat and UV light to monitor photosynthesis.

• UV light to detect body heat and infrared light to monitor photosynthesis.

• Visible light for illumination and UV light to check for skin damage.

​

Common Misconceptions

Misconception	Correction
All light from the sun is visible.	Visible light is a small part; the sun also emits UV and infrared rays.
You can't get a sunburn on a cloudy day.	Up to 80% of UV rays can pass through clouds, causing sunburn.
Light and sound are the same type of wave.	Light is an electromagnetic wave; sound is a mechanical wave.
Brighter light is always more powerful.	Light's energy depends on its frequency (color), not its brightness.

​

Summary

• Light is an electromagnetic wave that can travel through a vacuum.

• The electromagnetic spectrum organizes waves by their wavelength and energy.

• When light hits an object, it can be reflected, absorbed, or transmitted.

• Visible light powers photosynthesis, while UV light can damage our DNA.

Poll

On a scale of 1-4, how confident are you with the concepts covered in today's review lesson?

• 1 - Not confident at all

• 2 - A little confident

• 3 - Mostly confident

• 4 - Very confident