Waves transfer energy and interact in predictable ways. Behavior of Waves Waves transfer energy and interact in predictable ways.

Reflection When an object or a wave hits a surface through which it cannot pass, it bounces back. **1. Reflection is the bouncing back of a wave or object from a surface. For example, if you throw a ball at a wall, the ball bounces back. The ball is reflected by the wall.

Reflection **2. Sound waves bounce off walls and other hard surfaces. Reflected sound waves are called echoes.

Reflection ** 3. When reflection happens, light waves bounce off mirrors and other shiny surfaces. True or False: **4. You see your face in a mirror because light from your face bounces back from the mirror to your eyes.

Law of Reflection

Reflection

Review Questions The bouncing back of a wave or object from a surface is called An example of reflection. a. a pitcher throwing a ball b. a rocket flying into space c. an echo Is the following sentence true or false? You can see yourself in a mirror because of reflection.

Refraction **5. Refraction is the bending of a wave due to a change in speed. **6. Refraction happens only when a wave enters a new medium at an angle. **7. When a wave enters a new medium at an angle, one side of the wave changes speed before the other side, causing the wave to bend.

Refraction **8. Light travels slower through water than through air. So, when light enters water, it slows down.

Questions **Is the following sentence true or false? Reflection happens only when a wave enters a new medium at an angle.

2. The pictures show light waves moving from air into water 2. The pictures show light waves moving from air into water. Which picture shows refraction?

Transmission **9. A transmission of waves occurs when waves pass through a given point or medium. Sound waves are transmitted through solids, liquids, and gases.

**10. Light waves are transmitted through: Opaque materials allow no light waves to be transmitted through them. Translucent materials transmit some light, but cause it to be scattered so no clear image is seen.

**Light waves are transmitted through: Transparent materials (may be clear or colored material such as filters) that allow most of the light that strikes them to pass through them.

Absorption **11. Absorption of certain frequencies of light occurs when the energy is not transferred through, or reflected by, the given medium. (like a sponge) **12. Objects or substances that absorb any wavelength of electromagnetic radiation become warmer and convert the absorbed energy to infrared radiation.

Diffraction When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out. Diffraction is the bending and spreading out of waves. Diffraction happens when waves go around a barrier or through a hole in a barrier. Suppose that ocean waves hit a big ship. The ship is a barrier to the waves. The waves bend to travel around the ship. Then, the waves spread out across the water on the other side of the ship. The waves have been diffracted.

Questions 3. Is the following sentence true or false? The bending and spreading out of waves when they go around a barrier is called refraction.

4. The pictures show water waves reaching a hole in a wall 4. The pictures show water waves reaching a hole in a wall. Which picture shows how the waves will look after they go through the hole?