An object is located to the left of a convex lens whose focal length is 33 cm .

Question

An object is located to the left of a convex lens whose focal length is 33 cm . The magnification produced by the lens is m1 = 3.3.
To increase the magnification to 4.3, should the object be moved closer to the lens or farther away? Why?
Calculate the distance through which the object should be moved An object is located to the left of a convex lens whose focal length is 33 cm . The magnification produced by the lens is m1 = 3.3.
To increase the magnification to 4.3, should the object be moved closer to the lens or farther away? Why?
Calculate the distance through which the object should be moved An object is located to the left of a convex lens whose focal length is 33 cm . The magnification produced by the lens is m1 = 3.3.
To increase the magnification to 4.3, should the object be moved closer to the lens or farther away? Why?
Calculate the distance through which the object should be moved

Explanation / Answer

To calculate the inital object distance, we apply lens formula -1/f = 1/u +1/v

magnification m = -v/u = 3.3

v = -3.3 u

so now -f = uv/(u+v)

-f = u*-3.3u/(u-3.3u)

-f = 3.3u/2.3

so u = 2.3 f/3.3 = 2.3*33/3.3 = 23 cm

so initailly object is placed at 23 cm from the lens

now for m =-v/u = 4.3

v = -4.3u

so -f = u * (-4.3 u)/(u- 4.3u)

f = 4.3 u/3.3

u = 3.3 f/4.3

u = 3.3* 33/4.3

u = 25.33 cm

so object has to moved (25.33 -23) = 2.33 cm more away from the lens to get the desired magnification of 4.3

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