# Pixels, resoultion and light sensitive chips.

1. Oct 29, 2009

### greener1993

I have the answer to all theses questions beacuse they are from a book but don't quite understand how to get it. Nice and good to cheat on my homework but not good in exam :S i am just so confused. i understand the resoultion is the smallest thing you can see in the picture which in most cause is a pixel which also in most cases is 1MM long. However i cant seem to gather how to work out questions. Why not use the book? beacuse i swear to god it is useless. OCR advancing physics book. Its more of a history book about physics than anything that will get us a good grade.

LS= light sensitive.
Red = Word I do not understand or there relationship to the question

1)a digital camera has a lens of focus length 50mm and produces an image of 1280x960 pixels. A human face (270x200)that is 1.5mfrom the lens fills the picture Of the light sensitive chip.
A) Estimate the dimension of the picture area of the LS chip in the camera.
B) Estimate the dimensions of one picture element in the LS chip.
C) estimate the scale of features on the face that can be resolved in the picture. could a person eyelashes be resolved?

2) Estimate how many pixels are needed in a satellite image of a town, if parked cars are to be resolved in the image.
Information : town = 10km2
lenth of car = 3m
resoulution = 3m

3)Estimate how many pixels are needed in an ultrasound scan image of a full-term foetus, if the baby’s fingers are to be distinguished
Information : Width of finger is 3mm
length of foetus a few hundred mm

4) Estimate the dimensions of an area of space imaged around a star, if an Earth-sized planet is just detectable in a 100 M pixel image.
Informtaion : Earth is about 10 000 km in diameter.

I just need it explaining well. Would be nice if you could include any equations and step by step instructions

Thank you :)

Last edited: Oct 29, 2009