Spectral lines

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Courtesy of NOAO/AURA

Slide 20

Helium

The element Helium (He) was first discovered on the Sun by its spectral lines.

Slide 21

Doppler Shift

The Doppler Effect and Sonic Booms

Larry Sessions:

Image from: http://imagine.gsfc.nasa.gov/YBA/M31-velocity/doppler-shift-derive-2.html

Slide 22

Doppler Shift

The greater the velocity the greater the shift.

Slide 23

Concept Test

A car passes by blaring its horn. What do you hear?

A constant tone.

A tone that goes back and forth between high and low frequency.

A constant tone of lower intensity.

Two constant tones, one of higher frequency and one of lower frequency.

One tone going from smoothly from low to high intensity.

Larry Sessions:

Wav: http://www.kettering.edu/~drussell/Demos/doppler/carhorn.wav

Slide 24

Concept Test

I spin an object emitting a constant tone over my head. What do I hear?

A constant tone.

A tone that goes back and forth between high and low frequency.

A constant tone of lower intensity.

Two constant tones, one of higher frequency and one of lower frequency.

One tone going from smoothly from low to high intensity.

Slide 25

So Now…

From the presence and position of Spectral Lines we can know:

Composition (H, He, H2O, etc.)

Movement through space (towards or away)

How fast?