Astronomy and Cosmology 1

Astronomers use these terms to describe distance of stars to Earth

Light from the Sun takes ___________ to reach Earth.

• 480 seconds

• 8 seconds

• 8 lightyear

• 8 year

Definition for Luminosity (L):

Total​ (a)   of radiated by a star per unit ​ (b)   .

Unit for L : ​ (c)  

• energy
• time
• intensity
• power
• workdone
• watt
• watt/second

Definition for Radiant Flux Intensity (F)

Radiant ​ (a)   passing normally through a surface per unit ​ (b)   .

Unit for F: ​ (c)  

• power
• area
• intensity
• energy
• time
• watt
• w

A student observes different stars from the Earth. Give two reasons why some stars appear brighter than others.

1. Brighter star could be ​ (a)   to/from Earth.

2. Brighter star have ​ (b)   luminosity.

• closer
• far
• greater
• smaller