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Question from simple lens diagram (camera) 
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#1
May210, 01:21 PM

P: 342

1. The problem statement, all variables and given/known data
A simple camera has a converging lens of focal length 50.0 mm. It is used to photograph a tree 3.00 m high. The tree is 8.00 m away from the lens. Calculate the distance v between the lens and the film, giving your answer in mm to three significant figures. 2. Relevant equations 1/f = 1/u + 1/v 3. The attempt at a solution 1/50 = 1/8000 + 1/(v) v = 50.3 mm Is this correct? Thank you! 


#2
May210, 01:33 PM

P: 58

Why did you reason that the image distance was negative?



#3
May210, 01:57 PM

P: 342

Hmmm, not sure why I done that actually...
Have corrected to: 1/f = 1/u + 1/v 1/50 = 1/8000 + 1/v v = 50.3 mm 


#4
May210, 01:58 PM

P: 58

Question from simple lens diagram (camera)
That looks right. The negative image distance you got before implies that the film needed to be outside the camera to capture the image.



#5
May210, 02:06 PM

P: 342

Thanks Squeezebox!
When I want to calculate the linear magnification of the image, the following equation is used: m = v/u Do I use the same v and u values from above? (both in metres) i.e. 0.0503 / 8 = 0.0063 


#6
May210, 02:11 PM

P: 58

m= v/u The image gets flipped upside down. This happens with your eyes too; your brain flips the image back right side up. 


#7
May210, 02:28 PM

P: 342

Ah, so it'd be
0.0503 / 8 = 0.0063 So is the height of the tree, stated in the question as being 3.00 m, not required to obtain the linear magnification? 


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