Question

A thin lens with focal length f = +10.0 cm sits 5.0 cm away from an upright candle. The candle is sitting on the central axis and is 5.0 cm tall (including the flame). Using only a ray diagram and without doing any calculations, estimate: (a) the image distance (with correct sign) (b) the height of the image (including the flame) (c) whether the image is real or virtual (d) whether the image is upright or inverted

I can do the math on this one, but im having trouble with the diagram.

Answer 1

Here, is the ray diagram. Notice that i have used two rays to get the image formation.

Now, let's see if our ray diagram is correct

finding image distance

1/i = 1/f - 1/u

1/i = 1/10 - 1/5

i = -10 cm

so, yes our ray diagram shows correct position of image

let's now find magnification

m = - i / u

m - ( -10 ) / 5

m = 2

it means image is 2 times bigger than object which we can see in the diagram ( image height = 10 cm)

as magnification is positive, image is virtual and upright