Warm Up A pendulum with a length of

Warm Up • A pendulum with a length of 36. 9 cm has a period of 1. 22 sec. What is the gravitational field at the pendulum’s location?

WAVE The motion of a disturbance “Energy on the move” (not matter)

MEDIUM Material through which a wave travels

Some waves require a medium, others don’t!

MECHANICAL WAVE A wave that needs a medium to exist (ex: sound waves, water waves)

ELECTROMAGNETIC WAVE A wave that does not need a medium to exist (ex: light, UV, radio)

Electromagnetic Spectrum

2 Types of Waves • Transverse waves • Longitudinal Waves

Transverse Wave Particles vibrate perpendicular to the direction of wave motion

Longitudinal Wave Particles vibrate parallel to the direction of wave motion

Parts of a Wave • Crest • Trough • Wavelength • Amplitude

Crest Highest point of a wave

Trough Lowest point of a wave

Wavelength (l) Distance between 2 similar points of a wave (crest to crest)

Amplitude Distance from crest to equilibrium point (half the height)

Measurements of Waves

Period (T) The time it takes for one wavelength to pass a certain point T = 1/f

Frequency (f) Number of cycles per unit time (per second) Unit: Hertz (Hz) -1 Hz = s

Wave Velocity (V) V = fl The only variable that can change a wave’s velocity is the medium! (not amplitude, wavelength, or frequency)

Exit Question • Draw: – A transverse wave – A longitudinal wave

c = speed of light in a vacuum 8 = 3. 0 x 10 m/s (all electromagnetic waves travel at this speed)

Different Objects Respond to Light Waves in Different Ways

TRANSPARENT Material that transmits light rays such that the object can be clearly seen (Air, glass, some plastics)

TRANSLUCENT Material that transmits light rays, but the object can NOT be clearly seen (Lampshades, frosted bulbs)

OPAQUE Material that DOES NOT transmit light rays (bricks, tables)

Reflecting Material that reflects light waves (mirrors, shiny metal)

Luminous Illuminated