Sonar: SOund NAvigation and Ranging

Ships use reflected sound waves to locate objects underwater

Echolocation: Bats use reflected sound waves to navigate and hunt in the dark

Ultrasound: reflections of ultrasonic sound waves off of the soft tissues of the body are used to create an image

Can also use ultrasound to watch a person’s heart while it’s beating, to examine tumors, and to break up kidney stones.

A repeating movement or disturbance that transfers energy...

…through matter …or through space

Electromagnetic waves

Recall that both electrical charges and magnets have fields around them.

An electromagnetic wave is a double transverse wave that consists of both an electric and a magnetic field wave

Electromagnetic waves are transverse waves because the electric and magnetic fields vibrate in a direction perpendicular to the direction of travel.

Like all transverse waves, electromagnetic waves can be described in terms of their energy content, wavelength, frequency and wave speed.

Radiant energy: the energy content of an EM wave

Wave speed: the speed of EM waves depends upon the medium they’re travelling through. While they do not require matter to propagate, they do interact with matter which slows them down.

Vacuum: 300,000 km/s Water: 226, 000 km/s

Diamond: 124,000 km/s

R

O

Y

G

B

V(I)

Wavelength and Frequency of Visible light

Visible light is just a small portion of the EM spectrum

Wave nature of light

http://lectureonline.cl.msu.edu/~mmp/kap28/PhotoEffect/photo.htm

Photoelectric Effect

e

e e

e

Na metal

V

‘Particles’ of light are called photons

The light given off by elements when burning produces a line spectrum that can be used to identify the element.

Chapter 13: Light

Opaque: will not transmit light

Translucent: will transmit some light

Transparent: transmits almost all of the light

Transmission of light

Reflection of Light

Diffuse reflectionRegular reflection

Smooth surfaces will reflect the incident light waves in a single reflected beam.Ex: Driving at night on a WET road

Rough surfaces reflect the incident waves in many different directions.Ex. Driving at night on a DRY road

Refraction

Index of refraction: a number that indicates how much the light will bend when it goes from air to the new medium.

The higher the index of refraction, the greater the refraction angle

Prism: A prism separates the incident beam by wavelength.

The longest wavelengths (red) are refracted the least.

The shortest wavelengths (blue/violet) are refracted the most.