Waves, EM spectrum Mr. Sroka science

What is a wave?

A wave can be

described as an energy

disturbance that travels

through a medium from

one location to another.

Waves, simply put, are

energy moving from

one place to another.

How do they move?

As the wave moves through the medium (water, slinky, air), energy is being passed from one particle to the next. Waves occur around us every day. Some common places we experience waves are in sound, light, water, and earthquakes.

Two basic types of waves!

In a longitudinal wave

the particles move

parallel to the direction

the wave is moving.

In a transverse wave

the particles move at

right angles to the

direction of wave travel.

Wave characteristics!

Wavelength

Wavelength – The

length of a wave. This

can be measured easily

from crest to crest or

from trough to trough.

Frequency

Frequency – The

number of waves

produced in a given time

period. This is usually

measured in waves per

second called Hertz

(Hz).

Wave Speed v = c x f

Velocity = wavelength x frequency

This is the same formula we use for the speed of light

however the V gets changed to a lower case c.

Practice problems on the board!!!

Mechanical wave

Sound is a mechanical

wave that results from

the back and forth

vibration of the particles

of the medium through

which the sound wave is

moving.

Video

Electromagnetic Waves

EM waves for short

Electromagnetic waves are

waves which can travel

through the vacuum of outer

space.

Mechanical waves, unlike

electromagnetic waves,

require the presence of a

material medium in order to

transport their energy from

one location to another

Types of EM waves

Radio waves

Mircowave

Infrared waves

Visible light

Ultraviolet

X-rays

Gamma rays

What can we see???

LET THERE BE LIGHT!!!

Understanding the EM

spectrum allows

astronomers to study

the universe.

Think about it

Andromeda Galaxy is

roughly 2.5 million LYA.

For example The Sun The Sun emits lights in all

wavelengths – our eyes can only

see one small range of

wavelengths (i.e. visible light).

All the action takes place at the

wavelengths our eyes cannot

see. If you place different filters

over the cameras, you can

capture only the light that can get

through that filter.

We determine temperature of

distance objects this way

What else can we do?

Formation of a

Spectrum!

A spectrum splits light

into its wavelengths.

This is done by the use

of a spectroscope

Astronomers can use the spectral lines to

determine what stars and

galaxies are made of!

The Doppler Effect

The Doppler effect is

the change in frequency

of a wave for an

observer moving relative

to its source.

HUH??? It’s the change

in pitch you hear as an

ambulance passes.

Connection to Outer Space We can use the Doppler

effect to determine if things

are moving towards or away

from earth!

redshift/blueshift happens

when light or other

electromagnetic radiation

shifted to one end of the

spectrum.

Red longer away

Blue shorter towards

Summary - what can we

use star light for???

Temperature - Wein’s

law

Composition - spectral

lines

Direction and speed -

red/blue shift