Click and drag the candle on the right to see the image size, orientation and location of the candle's image.

When doing a light ray diagram there are generally two light rays.

1. The green light ray goes from the top of the candle parallel to the principle axis to the lens, then it goes through the focal point on the same side.
2. The red light ray goes from the top of the candle through the focal point on the other side of the lens, when it intersects the lens it then it goes parallel to the principle axis.

Where the two light rays cross marks the location of the image. If the image is on the opposite side of the lens than the object (candle) than it is a real image because you can put a screen there and get an object.

If the image is on the same side of the lens as the object than it is a virtual image because you can not put a screen there because the light hasn't gone through the lens. This is indicated by the dotted light ray lines.

Remeber diverging lenses have negative focal lengths.