Understanding Astronomy

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Slide 1

Light and Telescopes

Slide 2

What do you think?

What is the main purpose of a telescope?

Why do stars twinkle?

Slide 3

If you pass white light through a prism, it separates into its component colors.

R.O.Y. G. B.I.V

spectrum

Slide 4

If white light contains all colors, how fast does it move?

186,000 miles per second

300,000 kilometers per second

3 x 108 m/s

first successfully determined by Danish astronomer Ole Roemer in 1675

Slide 5

But, what is light?

In the 17th Century, Isaac Newton argued that light was composed of little particles while Christian Huygens suggested that light travels in the form of waves.

In the 19th Century, Thomas Young demonstrated that light bends slightly around corners and acts like interfering waves.

Slide 6

Thomas Young’s interference experiment

Slide 7

Scottish physicist James Clerk Maxwell showed mathematically in the 1860s that light must be a combination of electric and magnetic fields.

Slide 8

It wasn’t until 1905 that our current understanding of the nature of light emerged. Einstein showed that light sometimes behaves as particles and sometimes as waves.

Photon energy = Plank’s constant x speed of light / wavelength

Slide 9

Visible light is only one type of electromagnetic radiation emitted by stars

Each type of EM radiation travels at exactly the same speed - the speed of light!

Slide 10

Not all EM radiation can penetrate Earth’s atmosphere.

Slide 11

What is Light and Why Would Astronomers Want to Study the Properties of Light?

Sometimes we say light is made of waves

Sometime we say light is made of particles called photons

Moves very fast, at 186 000 miles per second

300,000 km per second

consider a prism .

Slide 12

If you pass white light through a prism, it separates into its component colors.