Question

Physics help: Number 4.

Laser 60- 4. (20 pts) A simple digital camera lens with a focal length 4.00 cm forms a sharp image of an objeto sensor screen located 14.0 cm from the lens. The object now moves away from the lens and the new distance required between the lens and sensor is 13.0 cm. a. Find the original distance from the lens to the object. b. By what amount did the object change its distance from the lens? c. Find the original magnification. Page 2 of 2

Answer 1

a)

using lens formula

1/f = 1/v - 1/u

1/ 4 = 1/14 + 1/u

u = 5.6 m

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b)

again

1/4 = 1/13 + 1/u'

u' = 5.778 m

so object moved by

d = 5.778 - 5.6 = 0.1778 m

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c)

original magnification

m = v/u = 14 / 5.6 = 2.5

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