A 4.0 cm -tall object is 12 cm in front of a converging lens that has a 20 cm fo
ID: 1446617 • Letter: A
Question
A 4.0 cm -tall object is 12 cm in front of a converging lens that has a 20 cm focal length. Part A Calculate the image position. Express your answer using two significant figures. s = cm SubmitMy AnswersGive Up Incorrect; Try Again; 4 attempts remaining Part B Calculate the image height. Express your answer using two significant figures. h = cm SubmitMy AnswersGive Up Provide FeedbackContinue Incorrect. Incorrect; Try Again; 4 attempts remaining. No additional feedback. Introductory Physics II- 10Z1_79696 Help Close 09: Refraction Problem 18.31 « previous 7 of 8 next »
Explanation / Answer
use the basic lens equation:
1/p + 1/q = 1/f
p=object distance = +12 cm
q=image distance
f=focal length = +20 cm
1/12 + 1/q = 1/20
q = -30 cm
q=30 cm, so the image is 30 cm behind the converging lens (the sign convention for converging lenses is that positive image distances are behind the lens; positive object distances are in front of the lens)
the magnification is given by m = -30/12 =-2.5
Height = (4.0 cm)*-2.5
= 10 cm (inverted)