P2 topic 13 exploring light

Question 1

What is the formula for working out the absolute magnitude

Answer 1

M = m - 5·log_10(d) + 5

Question 2

Describe how astronomers obtain the spectrum of a star.

Answer 2

Use diffraction grating (1)
connected to telescope (1)

Question 3

The spectrum of a star can be used to determine its chemical composition.
Explain how astronomers accomplish this.

Answer 3

From spectrum, obtain wavelengths of spectral lines (1)
Each chemical element has its own unique set of spectral lines (1)
Match the measured wavelengths to the known wavelengths of different
elements (1)

Question 4

State two stellar properties that can be determined from a star’s spectrum.

Answer 4

Temperature (1)
Radial velocity (1)
Spectral type / class (1)
If the star is moving away from or towards the observer(1)

Question 5

A teacher tells his students that the Earth’s atmosphere is responsible for two observing
‘windows’ .
Explain the meaning of the term ‘windows’.

Answer 5

Wavebands or region of wavelengths (1)…
…for which electromagnetic radiation reaches
ground / sea- level (1)

Question 6

State the two regions of the electromagnetic spectrum that correspond to the
‘windows’.

Answer 6

Radio (1)

Visible / optical (1)

Question 7

Explain why radio telescopes have much larger apertures than optical telescopes.

Answer 7

Resolution depends on aperture and

wavelength (1)
Radio waves have much longer wavelength than
visible light (1)

Question 8

State two advantages of using multiple radio telescopes that are connected in an array.

Answer 8

Any two from:

Higher / better resolution (1)
Ability to detect weaker sources of radio waves (1)
‘Observing’ times can be shorter for the same amount of data (1)
Allows collaboration between different groups of astronomers (1)