Characteristics of Waves Part II

Reflection When an object or a wave hits a surface through which it cannot pass, it bounces back. 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 Sound waves bounce off walls and other hard surfaces. Reflected sound waves are called echoes. Light waves bounce off mirrors and other shiny surfaces. You see your face in a mirror because light from your face bounces from the mirror to your eyes.

Reflection Law of Reflection - The angle of incidence is always equal to the angle of reflection.

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

Refraction Light travels slower through water than through air. So, when light enters water, it slows down. If a light wave passes from air into water - at an angle - one side of the light wave enters the water before the other side. This causes the light to bend.

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.

Interference There are two types of interference: constructive and destructive Interference is what happens between waves that bump into one another. When waves interfere, the waves combine to form a single wave.

Interference Constructive interference happens when the crests of one wave pass through the crests of another wave. The two waves combine to make a wave with a larger amplitude. Destructive interference happens when the crests of one wave pass through the low points of another wave. The two waves combine to make a wave with a smaller amplitude.

Types of Seismic Waves Seismic waves include P waves, S waves, and surface waves. Earthquakes cause waves that move through the ground. Earthquake waves are called seismic waves.

Types of Seismic Waves P (primary) waves are longitudinal waves. P waves move more quickly then other types of seismic waves. S (secondary) waves are transverse waves. S waves cannot travel through liquids, including Earth’s liquid outer core. Because of this, if you are on the other side of the planet, you can primarily only feel P waves. Surface waves are a combination of of longitudinal and transverse waves. Surface waves move more slowly then P waves or S waves. They also cause more damage than P waves or S waves.

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Types of Seismic Waves Tsunamis are huge surface waves in oceans. They are caused by underwater earthquakes.

Detecting Seismic Waves A seismograph records the ground movements caused by seismic waves are they move through Earth. Seismographs are instruments that measure earthquake waves. Seismographs can be used to find where an earthquake happened by measuring the time between a P wave and an S wave. Seismographs can also be used to find underground resources, such as oil and water.