Let there be light

1
Let there be light

• Most of what we know about the Universe comes
  from information that has been carried to us by
  light.
• We will begin by examining the properties of
  light and then we will discuss the instruments
  that are used to detect it (telescopes).t.

2
Light Basics

• Light is radiant energy
• Radiant energy is energy that can travel through
  space from one point to another without the need
  of a direct physical link
• In empty space light travels at a constant speed,
  299,792.458 kilometers per second (this is a
  constant and is denoted by c).
• Fast enough to circle the Earth over 7 times in
  one second!
• When light travels through matter, glass, water,
  gasses, etc. it slows down.
• Light can be thought of one of two ways
• 1. As an electromagnetic wave a mix of electric
  and magnetic energy

• 2. As photons photons are packets of energy
• Both models have one thing in common they
  classify light as being energy

3
Light As A Wave

• Parts of an electromagnetic wave
• Crest the high point of a wave
• Trough the low point of a wave
• Wavelength (?) the distance of two
  wavecrests or two wavetroughs

4
Looking At Waves Through Sound

• We cant see light waves, but we can look at
  sound waves to help us understand wave structure
  and wave energy.

• Which one of these wave models has the bigger
  wavelength?
• Which one of these models has the greater
  frequency?

5
The Difference Between Light and Sound Waves

• We use sound waves to hear. Even though sound has
  the same wave structure as light they are
  fundamentally different.
• Sound energy relies on the vibration of sound
  waves through matter.

• Light is a form of radiation
• It is not dependant on matter to get form one
  place to another.

6
Light is Radiation!!!! Oh No!!!!

• Yes, light is radiation. It is one of many types
  of radiation. All this means is that it can
  travel through space without the need for a
  direct transfer of energy.
• Sound was the opposite. It moves because of a
  direct transfer of energy from one particle to
  another

7
Types of Radiation