# Teacher Feature

## Curve Appeal

### Overview

Students will use the 2014 Baseball Hall of Fame commemorative coin to understand the terms "concave" and "convex."

### Activity

As a class, discuss the terms "concave" (curving inward or hollowed) and "convex" (curving outward).  Have the students share examples of items that are concave (spoon, bowl) and convex (ball).  Record the definitions and student responses on chart paper.  If possible, provide actual objects for the students to examine.

Display and discuss the features of convex and concave lenses.  Record on chart paper the students predictions of how objects will change when seen through the lenses.  If necessary, use car side-view mirrors or fun house mirrors to exemplify how curved glass changes appearances.

Distribute concave and convex lenses to students in pairs.  Have the pairs discuss how the shape of the lenses seems to change objects they examine through the lenses.

Have each student record personal observations about one object on a double T-chart.  Have them use the three columns to illustrate how the object looked originally, how it looked through the concave lens and how it looked through the convex lens.

Discuss the students' observations and compare them to the students' original predictions.  Invite students to share their illustrations with the class.

Display the 2014 Baseball Hall of Fame Commemorative Coin.  Tell the students the obverse (which is concave) features a glove and the reverse (convex) features a baseball similar to those used in Major League Baseball®

Read the March Coin of the Month to learn more about producing a coin with such a shape.  Have the students discuss and summarize how the concave and convex surfaces compliment their respective images.

As an extension, have the students write the words "concave" and "convex" in an imaginative way to visually help others remember the definitions.

### Make a Connection

Visit the Commemorative Coins page to learn more about the first curved set of coins from the United States Mint.

Visit the Baseball Hall of Fame site to get more information on the history of baseball, favorite players and more curriculum ideas for your classroom.

Visit the Kids' Baseball Coin Design Challenge page to see the winning designs that children ages 13 and under entered in the Kids' Baseball Coin Design Challenge.