Objectives:

1.    Describe a wave in terms of its frequency, speed, and amplitude.

2.    Identify the major regions of the electromagnetic specrtum.

Key Terms:

electromagnetic radiation    amplitude    wavelength    frequency    speed of light    visible spectrum

Web Resources:

Notes:

Waves and Energy:

Light travels in electromagnetic waves.  A wave is a disturbance that transfers energy through matter or space.    All waves can be characterized by the following four characteristics: amplitude, wavelength, frequency, and speed.

Characteristics of Waves:

All waves share certain characteristics:

# Amplitude

·         The maximum distance the molecules are displaced from their starting place

·        As energy ­, amplitude ­

(by Cattell and J. Dombeck (Univ of Minnesota) and M. Temerin and F. S. Mozer (Univ of Ca, Berkeley)

Wavelength

·        The distance between 2 consecutive crests or troughs

(imagers.gsfc.nasa.gov)

# Frequency

·        The number of cycles per unit time

·        Transverse – crests(troughs)/second

·        Compression – compressions(rarefactions)/second

·        Unit is the hertz (Hz)                        1Hz = 1wave/second

(www.lbl.gov/images)

Speed of Waves:

The speed of a wave is determined by the number of waves passing a point per second and the length of the wave.

·        Speed in any given medium is constant.

·        Speed = frequency · wavelength (f · l)

 If f ­,l¯ or f ¯, l ­

Waves through a medium:

A medium is any substance or region through which a wave is transmitted.

·        Solid, liquid, or gas

·        Transfers energy only without any net movement

2 properties of a medium affect wave speed

·        Density- ­ density slows the wave

·        Elasticity - ­ elasticity speeds up a wave

Light Energy:

The atom is the source of all light.

 When an atom absorbs electricity its electrons (e-) become excited The excited e- jumps to higher energy orbits As the excited e- looses energy, it falls back to its original orbit and releases a photon. A photon is a tiny packet or bundle of energy that contains the exact amount of energy that the atom absorbed.

·        The amount of energy a photon contains determines what type of light is emitted

(www.yorku.ca)

Electromagnetic Waves: (Light)

·        All forms of light travel at 3x108 m/s in a vacuum

·        Light requires no medium

·        All electromagnetic waves are transverse waves

·        2 waves- Electric wave & Magnetic wave

·        Waves are at 90o angles