× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
Home Q & A Board Science-Related Homework Help Physics
New Topic  
adelinetohyj adelinetohyj
wrote...
Posts: 6
Rep: 0 0
9 years ago
A 100 W light bulb is 20% efficient (i.e. 80% of its output is invisible infra-red
radiation and only 20% is visible light). A person can see the light with the naked
eye from a distance of 10 km on a dark night. If the area of the pupil of the persons
eye is 0.50 cm2, what power of the visible light is received by the eye of the person?
(A) 2.4×10−16 W
(B) 8.0×10−13 W
(C) 1.5×10−12 W
(D) 2.0×10−9 W
(E) 8.0×10−9 W
Read 390 times
1 Reply

Related Topics

Replies
wrote...
#1
Educator
9 years ago
Quote from: adelinetohyj (9 years ago)
(B) 8.0×10−13 W
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  1280 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Related Images
  
 248
  
 347
  
 269
Your Opinion
What's your favorite funny biology word?
Votes: 328
Previous poll results: Which industry do you think artificial intelligence (AI) will impact the most?