Light Lab Guide: Bending, Bouncing, & Beyond!

Welcome, Light Explorers! In this lab, you will investigate four amazing properties of light: Reflection, Refraction, Diffraction, and Scattering. Work carefully with your group at each station and record your observations on your Light Properties Worksheet.

Station 1: Reflection - The Bounce Back!

Materials: Flashlight/laser, plane mirror, piece of white paper, protractor (optional)

Procedure:

1. Place the mirror upright on a flat surface.
2. Shine the flashlight or laser beam towards the mirror.
3. Observe how the light beam bounces off the mirror.
4. Try changing the angle at which you shine the light at the mirror. What happens to the reflected beam?
5. Place a small object (like a coin) in front of the mirror. Observe its reflection.

Questions for your Worksheet:

• Describe what happens to light when it hits a mirror.
• How does the angle of the incoming light affect the angle of the reflected light?
• Where do you see reflection in your daily life?

Station 2: Refraction - The Bending Light!

Materials: Clear glass/beaker, water, pencil, flashlight/laser, prism

Procedure:

1. Fill the clear glass with water.
2. Place a pencil into the water at an angle. Observe the pencil from the side and from the top.
3. Shine the flashlight or laser through the side of the glass of water. Observe the path of the light.
4. Carefully shine the flashlight or laser through the prism. What do you observe about the light that comes out?

Questions for your Worksheet:

• Describe how the pencil appears when placed in water. Why do you think it looks this way?
• What happens to the light beam as it passes from air into water (or glass)?
• What colors do you see when light passes through the prism? What does this tell you about white light?

Station 3: Diffraction - The Spreading Wave!

Materials: Flashlight/laser, small comb (or diffraction grating), cardboard with a narrow slit, white paper/screen

Procedure:

1. Hold the comb (or diffraction grating) close to your eye and look through it at a distant light source (like a bare light bulb across the room, not the laser).
2. What patterns or colors do you see around the light source?
3. Hold the piece of cardboard with the narrow slit in front of your flashlight/laser. Shine the light through the slit onto a white paper or screen.
4. Observe the light pattern that forms. Is it just a single line, or something else?

Questions for your Worksheet:

• Describe the patterns you saw when looking through the comb/diffraction grating at a light source.
• What did the light look like after passing through the narrow slit? Did it spread out?
• In your own words, explain what diffraction means.

Station 4: Scattering - The Light Show!

Materials: Clear plastic cup, water, a few drops of milk (or a pinch of cornstarch), flashlight/laser, dark background (optional)

Procedure:

1. Fill the clear plastic cup with water.
2. Shine the flashlight or laser beam through the clear water. Observe the path of the light. (It should be mostly invisible).
3. Add a few drops of milk or a pinch of cornstarch to the water and stir gently until it mixes well (the water should become slightly cloudy).
4. Now, shine the flashlight or laser beam through the milky water again. Observe the path of the light and the color of the scattered light.
5. Look at the milky water from the side where the light enters, and then from the side where the light exits. Do you see different colors?

Questions for your Worksheet:

• What was different about the light beam in clear water versus milky water?
• What color did the light appear to be when scattered by the milk particles (looking from the side)?
• Why do you think the sky is blue and sunsets are red? (Hint: Think about scattering!)

Light Properties Worksheet: Your Lab Journal

Name: ____________________________

Date: ____________________________

Follow the instructions in your Light Lab Guide and record your observations and answers below. Be thorough and describe what you see!

Station 1: Reflection - The Bounce Back!

Observations: Describe what happens when light hits the mirror and how changing the angle affects the reflected light.

Questions:

1. Describe what happens to light when it hits a mirror.
   
   
   
   
2. How does the angle of the incoming light affect the angle of the reflected light?
   
   
   
   
3. Where do you see reflection in your daily life? List at least two examples.
   
   
   
   
   
   
   

Station 2: Refraction - The Bending Light!

Observations: Describe how the pencil appears in water, what happens to the light beam in water, and what you see with the prism.

Questions:

1. Describe how the pencil appears when placed in water. Why do you think it looks this way?
   
   
   
   
   
   
   
2. What happens to the light beam as it passes from air into water (or glass)?
   
   
   
   
3. What colors do you see when light passes through the prism? What does this tell you about white light?
   
   
   
   
   
   
   

Station 3: Diffraction - The Spreading Wave!

Observations: Describe the patterns you saw when looking through the comb/diffraction grating and the pattern formed by light passing through the narrow slit.

Questions:

1. Describe the patterns you saw when looking through the comb/diffraction grating at a light source.
   
   
   
   
   
   
   
2. What did the light look like after passing through the narrow slit? Did it spread out?
   
   
   
   
3. In your own words, explain what diffraction means.
   
   
   
   
   
   
   

Station 4: Scattering - The Light Show!

Observations: Describe the difference between the light beam in clear water versus milky water, and any color differences you observed.

Questions:

1. What was different about the light beam in clear water versus milky water?
   
   
   
   
2. What color did the light appear to be when scattered by the milk particles (looking from the side)?
   
   
   
   
3. Why do you think the sky is blue and sunsets are red? (Hint: Think about scattering!)
   
   
   
   
   
   
   

Light Properties Answer Key

This answer key provides expected responses for the Light Properties Worksheet. Student answers may vary slightly but should capture the core concepts.

Station 1: Reflection - The Bounce Back!

Expected Observations: Students should observe that light bounces off the mirror. When the angle of the incoming light (incident ray) changes, the angle of the reflected light also changes proportionally.

Questions:

1. Describe what happens to light when it hits a mirror.

   • When light hits a mirror, it bounces off the smooth, shiny surface. This bouncing back of light is called reflection.

2. How does the angle of the incoming light affect the angle of the reflected light?

   • The angle of the reflected light is equal to the angle of the incoming light relative to the surface's normal (an imaginary line perpendicular to the surface). If you shine the light straight on, it reflects straight back. If you shine it at an angle, it reflects at the same angle on the other side.

3. Where do you see reflection in your daily life? List at least two examples.

   • Examples include looking in a mirror, seeing your reflection in a window, reflections on a calm water surface, shiny objects like polished chrome, or reflective road signs.

Station 2: Refraction - The Bending Light!

Expected Observations: Students should see the pencil appear "bent" or displaced at the water line. The light beam will appear to change direction as it enters the water, and the prism will separate white light into a spectrum of colors.

Questions:

1. Describe how the pencil appears when placed in water. Why do you think it looks this way?

   • The pencil appears bent or broken at the point where it enters the water. This happens because light travels at different speeds in air and water. When light passes from one medium to another, it changes speed and direction, causing the pencil to appear distorted.

2. What happens to the light beam as it passes from air into water (or glass)?

   • The light beam changes direction, or bends. This phenomenon is called refraction.

3. What colors do you see when light passes through the prism? What does this tell you about white light?

   • Students should observe the colors of the rainbow (red, orange, yellow, green, blue, indigo, violet). This demonstrates that white light is actually composed of all these different colors of the visible spectrum.

Station 3: Diffraction - The Spreading Wave!

Expected Observations: When looking through the comb/diffraction grating, students should see patterns of light, possibly with rainbow-like fringes or multiple light sources. When light passes through the narrow slit, it will spread out, forming a wider band of light or even multiple bright and dark bands, rather than just a sharp line.

Questions:

1. Describe the patterns you saw when looking through the comb/diffraction grating at a light source.

   • Students should describe seeing multiple images of the light source, or a spectrum of colors spread out from the light. This is due to the light waves bending and interfering as they pass through the small gaps.

2. What did the light look like after passing through the narrow slit? Did it spread out?

   • The light beam should have spread out after passing through the narrow slit, appearing wider than the slit itself. It might also show faint lines or bands on either side of the central bright band.

3. In your own words, explain what diffraction means.

   • Diffraction is the bending and spreading of light waves as they pass through a small opening or around the edges of an obstacle. It causes light to spread out rather than travel in a perfectly straight line when encountering barriers.

Station 4: Scattering - The Light Show!

Expected Observations: In clear water, the light beam will be mostly invisible. In milky water, the light beam will become visible as it passes through. When looking from the side, the scattered light might appear bluish. When looking directly through the cup, the light might appear reddish/yellowish.

Questions:

1. What was different about the light beam in clear water versus milky water?

   • In clear water, the light beam was almost invisible. In milky water, the light beam became visible because the tiny milk particles scattered the light in all directions.

2. What color did the light appear to be when scattered by the milk particles (looking from the side)?

   • The scattered light (when viewed from the side) typically appears bluish. This is because smaller wavelengths of light (like blue) are scattered more effectively by the small particles.

3. Why do you think the sky is blue and sunsets are red? (Hint: Think about scattering!)

   • The sky is blue because tiny particles and molecules in the Earth's atmosphere scatter shorter-wavelength blue light more efficiently than longer-wavelength red light. So, when we look at the sky, we see scattered blue light. During sunsets, the sun's light has to travel through more of the atmosphere. Most of the blue light has been scattered away, allowing more of the longer-wavelength red and orange light to reach our eyes directly, making the sunset appear red.