A converging lens is used to project a 250 mm image of a square slide onto a screen 1000 mm away. the focal length of the lens is 200 mm. by means of scale drawing, determine---(a) the distance of the slide from the lens----(b) the size of the slide???

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Answer 1 · 2016-06-30T17:25:08

(a)Distance of the slide from lens = 250 mm

(b) The size of the slide = 62.5 mm

self drawn

Given

We are to find out

Calculation

Lens formula

$color(blue)(1/v-1/u=1/f)$

Plugging the values

$=>1/1000-1/u=1/200$

$=>1/u=1/1000-1/200=(1-5)/1000=-1/250$

$color(red)(=>u=-250mm)$

$color(green)("-ve sign means real object")$

Now magnification (m)

$m = s_i/s_o=v/u$

$=>250/s_o=1000/250=4$

$color(red)(=>s_o=250/4=62.5mm)$

The distance of the slide from lens (u)=250mm.

The size of the slide =62.5mm