Activity 1.7 - Exploring refraction

• Understanding that light is refracted when it travels from one medium to another
• Understanding that light can be reflected from and transmitted through an interface

• Laser pointers (red, low wattage), large plastic lunch boxes with transparent/semi-transparent walls, salt or milk, water, plastic sheets (e.g. bin bags), plastic spoons, green or blue laser pointer

The plastic sheets are placed on the desks in case of spillage. Students fill a plastic lunch box with water and add salt or milk until the water appears cloudy. Plastic spoons can be used in the case of salt to agitate the water during the investigations. The lunch box should be positioned close to the edge of the desk to allow for a wide range of possible angles.

The students begin by shining the laser pointers from air into the water and investigating how the path of light alters as they change the angle. They should draw a diagram to illustrate what they observe.

Next they investigate how the path of light changes if they shine the laser pointer through the side of the lunch box, through the water, and into the air. Again, they should draw a diagram to illustrate what they observe.

The teacher should then use the green or blue pointer side-by-side with a red pointer to illustrate that light of different colours will refract by different amounts.

• How does the direction of light change when it travels from air into water?
• How does the direction of light change when it travels from water into air?
• Is it possible to pick an angle so that light travelling from water into air is reflected from the interface between the media?
• Why is not possible to see the beam of laser light passing through the air when it can be seen passing through the water?
• Why does a prism disperse white light into its constituent colours?