Using Radiation to Investigate Stars (Unit 1)

Question 1

What does the stellar spectrum consist of?

Answer 1

-a star emits light as a continuous spectrum, from the dense gas of the surface of the star

Question 2

Where do black lines of a line absorption spectrum come from?

Answer 2

• light must pass through the gasses in the star’s TENOUS atmosphere
  -where the atoms in the gas absorb some wavelengths of light leaving absorption lines to be superimposed on the spectrum

Question 3

Black bodies definition?

Answer 3

A body which absorbs all the incident radiation that falls upon it

Question 4

What is a good example of a black body?

Answer 4

-stars are very good approximations to black bodies

Question 5

When we look at light emitted from a star what do we see?

Answer 5

• a continuous spectrum (i.e. all colours, all wavelengths)

Question 6

Features of black body spectrum?

Answer 6

-peak wavelength is inversely proportional to the absolute temperature
- higher temp, peak intensity happens at lower wavelength

Question 7

How to work out luminosity per second of a star?

Answer 7

Using Stefan’s constant
-power = luminosity per second
-Unit = Watt

Question 8

What does A equal in Stefan’s constant?

Answer 8

-Surface area

Question 9

Relative Luminosity?

Answer 9

Power/Luminosity

Question 10

Surface area of sphere?

Answer 10

4 pi r^2

Question 11

Wein’s law? words

Answer 11

-The wavelength of peak emission from a black body is inversely proportional to the absolute temperature of the body

Question 12

Use equation to define Stefan’s law?

Answer 12

-The power per unit area of a blackbody is directly proportional to it’s absolute temp to the power of 4

Question 13

Intensity Units?

Answer 13

Pm^-2

Question 14

Intensity equation?

Answer 14

Intensity = Power / 4 pi r^2

Question 15

Compare intensity of two stars from same source? equation

Answer 15

i 1 x (r 1)^2 = i 2 x (r 2)^2

Question 16

What is multiwavelength astronomy?

Answer 16

-Studying stars and space by making observations outside of the visible light spectrum can give more information about the processes which took place

Question 17

Intensity word?

Answer 17

-amount of light energy striking each square metre per second’

Question 18

Luminosity of a star word equation?

Answer 18

total energy a start emits per unit time in the form of electromagnetic radiation

Question 19

Example of multi wavelength astronomy?

Answer 19

observing using the microwave region of the spectrum revealed the cosmic microwave background radiation