Wave Properties: Crests and Troughs

Understanding the anatomy of waves Exploring how waves move energy Grade 7 Science

What Do You Already Know?

Think about waves you've seen in your daily life Where do you encounter waves? What do you notice about their movement?

What is a Wave?

A disturbance that transfers energy through matter or space Waves carry energy, not matter The medium (water, air, etc.) moves up and down, but doesn't travel forward Examples: water waves, sound waves, light waves

Anatomy of a Wave

Crests: The Wave Peaks

The highest point of a wave Where the wave displaces the medium the most upward In ocean waves, crests are where you see white foam The distance between crests determines wavelength

Troughs: The Wave Valleys

The lowest point of a wave Where the wave displaces the medium the most downward In ocean waves, troughs appear as the 'valleys' between waves Surfers often ride in the trough of large waves

Comparing Crests and Troughs

{"left":"Crests are the highest points\nMaximum upward displacement\nWhere wave energy peaks\nOften visible as foam in water","right":"Troughs are the lowest points\nMaximum downward displacement\nWhere wave energy dips\nAppear as valleys between waves"}

Wave Motion Simulation

Stand up and form a line Practice making a 'human wave' Notice: you move up and down, but stay in place The wave motion travels along the line Identify who represents crests and troughs at different times

Waves in Different Mediums

Water waves: visible crests and troughs on the surface Sound waves: air pressure creates invisible crests and troughs Light waves: electromagnetic crests and troughs we can't see All waves have the same basic properties

Check Your Understanding

If you're floating on a wave, what happens when a crest passes under you? What would you observe at a trough? Why don't you move forward with the wave? How can you measure the distance between two crests?