Problem: A student is working in an optics lab and has a light bulb which is 90 cm from a screen. She needs to make a real image of the bulb on the screen and she has a positive lens with a focal length of 12.5 cm. Find two places she can put the lens and give object and image distances to both setups.

FREE Expert Solution

Len's equation,
1f=1si+1so

Quadratic formula,

x=-b±b2+4ac2ab

f = 12.5 cm

so = so

si = (90 - so) cm

112.5=1so+190 - so112.5=(90 - so)+(so)(so)(90 - so)112.5=9090so - so290so - so2=90×12.50=so2-90so+1125

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Problem Details

A student is working in an optics lab and has a light bulb which is 90 cm from a screen. She needs to make a real image of the bulb on the screen and she has a positive lens with a focal length of 12.5 cm. Find two places she can put the lens and give object and image distances to both setups.