Edible Optics

Lens Lollipop Lesson Plan!

(We developed this in collaboration with a 1^st/2^nd grade Gifted and Talented teacher in Tucson)

Suggested time: 30 minutes

Grade range: 1^st-5^th

Materials: Assorted lens lollipops – at least one for each student, with a few extras in case the students want to look through multiple lenses at once.

Vocabulary: Lens, magnifying, minifying, nearsighted, farsighted, focus

Optional vocabulary: Convex, concave, radius of curvature, focal length, spherical

Before you begin: Tell the students to hold the lollipops by the stick to avoid getting the lenses dirty. Tell the students that they will be able to eat the lollipops at the end of the lesson, so they should be careful not to break or drop the lollipops.

At the beginning of the lesson, hand out lens lollipops to all of the students and encourage them to use their lens to explore their surroundings (anything from their desks to the entire classroom, depending on class size). You might want to demonstrate activities for them to try using your own lens. After a couple of minutes, ask the students what they’ve noticed.

If a student says that their lens makes things look bigger, ask the class if they’ve used anything else that can do that. A student will probably bring up magnifying glasses, or you can describe a magnifying glass (a large round lens with a handle that detectives use to make things look larger). Tell the students that lenses that make things look larger are called magnifying lenses. Ask a student with a magnifying lens to draw a side-view of their lens on the board, or draw one yourself.

 (Two examples of magnifying lenses)

If the students have previously learned about convex and concave polygons (3^rd grade in some states), you can tell them that this shape of lens is called ‘convex’.

If a student says that their lens makes things look smaller, ask the class if they’ve used anything else that can do that. A student might mention that they’ve looked through a pair of glasses that makes everything smaller. If no one has seen this type of lens before, just explain that lenses that make things look smaller are called minifying lenses. Ask a student with a minifying lens to draw a side-view of their lens on the board, or draw one yourself.

 

(Two examples of minifying lenses)

If the students have previously learned about convex and concave polygons, you can tell them that this shape of lens is called ‘concave’.

Encourage the students to trade lenses with someone with the opposite lens type (have the extra lenses on hand in case the students received an unequal number of magnifying and minifying lenses). As they continue to explore, suggest that they try looking through multiple lenses at once (stacked on top of each other), comparing two of the magnifying or two minifying lenses side by side, and holding their lens at different heights above their desk and looking at the pattern the light going through the lens makes on the desk.

If anyone in the classroom wears glasses, ask permission to use their glasses at this point in the lesson. Test what type of glasses they have by checking whether the lenses are magnifying or minifying. If the lenses magnify, their owner is farsighted, meaning that they need help seeing things that are close to them. If the lenses minify, their owner is nearsighted, meaning that they need help seeing things that are far away.

To help the students understand how glasses help people see, you can add these lines to your lens drawings:

  

The magnifying lens sends all the light to the same point – it focuses the light. Some students might have noticed that the magnifying lenses created small, bright spots on their desks when held at the right height above the desk. These spots appear because the lens is focusing the light from the ceiling lights. Farsighted people have eyes that need help focusing the light, so they wear magnifying lenses.

The minifying lens spreads the light out. If the students hold the minifying lenses above their desks, they’ll see a dark circle beneath the lens. Nearsighted people have eyes that focus light too early, so they wear minifying lenses to spread the light out.

Ask the students if they noticed anything when they compared different lenses of the same type. A student may have noticed that lenses that are more curved are better at magnifying or minifying. If not, take two magnifying lenses with different curvatures and hold them over a book to show that the title looks larger through the lens that is more curved. You can add these diagrams to the board to help explain:

 

If the students have learned about the radius of a circle (again, around 3^rd grade), you can explain that each lens has a radius of curvature. Draw a small circle and a large circle on the board, draw the radius of each circle, and draw a line through each circle to create a magnifying lens shape from the circle. Point out that the circle with a larger radius results in a lens that is less curved, so a smaller radius of curvature results in a more powerful lens. This can also be described in terms of focal length. A lens with a shorter radius of curvature will also have a shorter focal length.

 

As you explain radius of curvature, you can also explain that these lenses are spherical. The magnifying lenses would become solid spheres if their curve continued, and the minifying lenses would become hollow spheres.

After a few more minutes of letting the students explore with their lenses, you can wrap up the lesson. For 1^st and 2^nd graders, an effective wrap-up activity is to collect all the lenses and ask questions to check what the students have learned. Whenever a student answers a question correctly, let the student select a lollipop to eat. If you run out of questions before all of the students have received a lollipop, you can ask where students have encountered lenses before or whether they have any other observations or questions.

Potential short homework assignments:

• Ask students to find a family member or friend with glasses and figure out what type of lenses the person uses.

• Ask students to find an example of lenses around their house.

• For higher grades, you can ask the students to think about curved mirrors using what they learned about lenses. If desired, mirrors can then be covered as a separate lesson.