1-4. The graph below shows the how the intensity of radiation varies at different wavelengths for a given body.

black body curve

  

1. Which of the answers below best describes this radiation spectrum?

  • A. The emission of radiation at different wavelengths from a perfect black body.
  • B. The absorption of radiation at different wavelengths from a perfect black body.
  • C. The emission of radiation at different wavelengths from a perfect white star.
  • D. The absorption of radiation at different wavelengths from a perfect white star.

2. The radiation graph shown above is characteristic of a certain temperature. What happens to the height and position of the peak as the temperature falls?

Height of peak at lower temperature position of peak at lower temperature
A
 Higher peak moves to the left
B
 Higher peak moves to the right
C
 Lower peak moves to the right
D
 Lower peak moves to the left

3. The peak wavelength in the graph above is at a wavelength of 2.9 x 10-6 m. This corresponds to a temperature of....

  • A. 10 3  oC
  • B. 10-3  oC
  • C. 10-3  K
  • D. 10 3  K

4. This peak wavelength in the graph above can explain the colour of stars. Which of these statements is correct?

  • A. A red star is hotter than a blue star because the peak is at a shorter wavelength
  • B. A red star is hotter than a blue star because the peak is at a longer wavelength
  • C. A red star is cooler than a blue star because the peak is at a shorter wavelength
  • D. A red star is cooler than a blue star because the peak is at a longer wavelength

5. Here are three measurements taken on stars:

I. The total power output at all wavelengths of radiation
II. The power output at a specific wavelength of radiation
III. The intensity of radiation received by an observer, in watts per meter squared.

Which of these statements best describes apparent brightness and luminosity?

 
Brightness Luminosity
A
 I II
B
 I III
C
 III II
D
 III I

 

6+7. The image shows an illustration of two stars of the same apparent brightness.

The red star is further away than the white star.

 two stars compared

6. The red star has..

  • A. a lower temperature and a lower luminosity
  • B. a lower temperature and a higher luminosity
  • C. a higher temperature and a lower luminosity
  • D. a higher temperature and a higher luminosity

7. The white star is at a distance d and has a luminosity L. The red star is at distance 2d, and therefore has a luminosity of ..

  • A. 2L
  • B. 4L
  • C. ½L
  • D. ¼L

8-10: Another two stars are compared. Both stars have the same luminosity.

Star X Star Y
Luminosity = L Luminosity = L
Brightness = 4b Brightness = b
Temperature = T Temperature = ½T
Surface area = S Surface area = ?
distance = d distance = ?
 

8. Star X appears as a white star, with a peak wavelength in the middle of the visible spectrum. Star Y is likely to have a peak in which region of the electromagnetic spectrum?

  • A. infrared
  • B. ultraviolet
  • C. microwave
  • D. X-ray

9. The surface area of star Y is:

  • A. 4S
  • B. 8S
  • C. 16S
  • D. 32S

10. The distance to star Y is:

  • A. 2d
  • B. 8d
  • C. ½d
  • D. ¼d

By ESO/G. Beccari CC BY 4.0