Practice QuestionsElectromagnetic Spectrum

The electromagnetic spectrumFigure 3.5

Identify the following portions of theElectromagnetic spectrum:

A B D EC

The electromagnetic spectrumFigure 3.5

Which end of the spectrum is more energetic, A or B? Why?

A B

Light has a DUAL NATURE!

“photon”wave

&

If the Hydrogen

gas cloud is moving towards

Earth, the absorption line marked will shift in

which direction?

BA

An absorption line of Hydrogen measured at rest

How do light and matter interact?KNOW THESE DEFINITIONS!

• Emission

• Absorption

• Transmission

• Reflection or Scattering

What types of light spectra can we observe?

1. Continuous spectra

2. Absorption spectra

3. Emission spectra

Which is the absorption spectrum?

Which is the continuous spectrum?

Which is the emission spectrum?

BLUE

Yellow

RED

BLACK

Which spectrum is coming from the coolest object?

BLUE

Yellow

RED

BLACK

The object producing the yellow spectrum might be what type of star?

BLUE

Yellow

RED

BLACK

Is the star producing the yellow or red spectrum hotter? Why?

BLUE

Yellow

RED

BLACK

Which spectrum is coming from the hottest object?

Which star is more luminous?

T = 15,000 KRadius = 1 unit T = 15,000 K

Radius = 2 units

Which star is more luminous?

T = 3,000 KRadius = 1 unit

T = 15,000 KRadius = 1 unit

REMEMBER!

Luminosity of a star is intrinsic.

Depends on Temperature & Radius.

For which stars would we observe a Doppler Shift?

A

B

C

Doppler shiftFigure 3.18

Doppler Effect Summary

Motion toward or away from an observer causes a

shift in the observed wavelength of light:

• blueshift (shorter wavelength)

motion _______ you

• redshift (longer wavelength) motion AWAY

from you

• greater shift greater speed

Doppler Effect Summary

Motion toward or away from an observer causes a

shift in the observed wavelength of light:

• blueshift (shorter wavelength) motion toward

you

• redshift (longer wavelength)

motion ______ from you

• greater shift greater speed

How do telescopes help us learn about the universe?

• Telescopes collect more light than our eyes

light-collecting area

• Telescopes can see more detail than our eyes angular resolution

• Telescopes/instruments can detect light that is invisible to our eyes (e.g., infrared, ultraviolet)

The energy source for the sun is

• A. combustion of hydrocarbons

• B. solar flares

• C. nuclear fission, the splitting of two

hydrogen atoms

• D. nuclear fusion, the joining of two

hydrogen atoms

• E. combustion of hydrogen

The energy source for the sun is

• A. combustion of hydrocarbons

• B. solar flares

• C. nuclear fission, the splitting of two

hydrogen atoms

• D. nuclear fusion, the joining of two

hydrogen atoms

• E. combustion of hydrogen

The hotter an object

• A. the brighter it appears at all wavelengths, and the longer the wavelength at which it appears brightest• B. the shorter the wavelength at which it appears brightest• C. The brighter it appears at all wavelengths, and the shorter the wavelength at which it appears brightest• D. the longer the wavelength at which it appears brightest• E. the brighter it appears at all wavelengths

The hotter an object

• A. the brighter it appears at all wavelengths, and the longer the wavelength at which it appears brightest• B. the shorter the wavelength at which it appears brightest• C. The brighter it appears at all wavelengths, and the shorter the wavelength at which it appears brightest• D. the longer the wavelength at which it appears brightest• E. the brighter it appears at all wavelengths

An object emits an emission line spectrum. If the object moves towards

an observer,• A. the observed emission lines shift to

shorter wavelengths

• B. the observed emission lines shift to longer

wavelengths

• C. the emission line spectrum shifts to a

continuous spectrum

• D. the emission line spectrum shifts to

an absorption line spectrum

An object emits an emission line spectrum. If the object moves towards

an observer,• A. the observed emission lines shift to

shorter wavelengths

• B. the observed emission lines shift to longer

wavelengths

• C. the emission line spectrum shifts to a

continuous spectrum

• D. the emission line spectrum shifts to

an absorption line spectrum

Which of the following is ordered by increasing wavelength?

• A. infrared, visible, radio, gamma-ray

• B. visible, infrared, radio, gamma-ray

• C. gamma-ray, visible, infrared, radio

• D. radio, visible, infrared, gamma-ray

Which of the following is ordered by increasing wavelength?

• A. infrared, visible, radio, gamma-ray

• B. visible, infrared, radio, gamma-ray

• C. gamma-ray, visible, infrared, radio

• D. radio, visible, infrared, gamma-ray

An atom is ionized if

• A. it has lost a proton

• B. it has lost an electron

• C. it has lost a neutron

• D. it has absorbed a photon

An atom is ionized if

• A. it has lost a proton

• B. it has lost an electron

• C. it has lost a neutron

• D. it has absorbed a photon