Question

ncoming parallel rays of light such as from the Sun pass through a lens and form a real, inverted image with an image distance of 85.0 cm. You then hold the same lens 2.00 m in front of a painting, which is the object. What will be the image distance of the painting?

	A.	1.28 m
	B.	-0.596 m
	C.	-2.05 m
	D.	0.850 m
	E.	None of these answers

Answer 1

We have the lens formula

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$

When rays are coming from the sun so we have $u = \infty$ for parallel rays so

$\frac{1}{85} - \frac{1}{\infty} = \frac{1}{f}$

$\frac{1}{85} = \frac{1}{f}$

Now the same lens is placed 2 m infront of a painting so

u = -2m

$\frac{1}{v} +\frac{1}{2} = \frac{1}{0.85}$

option E , none of the above