2.12 - Real and Virtual Images

What can the images formed by a lens be?

• upright or inverted (upside down compared to the object)

• magnified or diminished (smaller than the object)

• real or virtual

What is a real image?

an image that is formed where the rays of light are focused

What is a virtual image?

an image that appears to be coming from behind the lens

What can a real image do?

be projected onto a screen

Where does a virtual image appear to be coming from?

behind the lens

How do you draw a ray diagram?

1. Draw a ray from the object to the lens that is parallel to the principal axis. Once through the lens, the ray should pass through the principal focus.

2. Draw a ray which passes from the object through the centre of the lens.

What are images formed by a convex lenses?

• a camera

• a human eye

• projectors

• magnifying glasses

What are images formed by a concave lenses?

peep hole lenses

What does an image for a distant object that is placed more than twice the focal length from the length look like?

• inverted

• diminished

• real

What does this diagram show?

ray diagram for an object placed more than two focal lengths away from a convex lens

What does an image for an object placed between one and two focal lengths from the lens look like?

• inverted

• magnified

• real

What does this diagram show?

ray diagram for an object placed between 2F and F from a convex lens

What does an image for an object placed at a distance less than the focal lengths look like?

• upright

• magnified

• virtual

What does this diagram show?

ray diagram for an object placed less than one focal length from a convex lens

What images do concave lenses always produce?

• upright

• diminished

• virtual

What does light rays do when an object is viewed through a concave lens?

light rays from the top of the object will be refracted and will diverge on the other side of the lens

What does an image for an object viewed through a concave lens look like??

• from the same side of the principal axis meaning the image will be upright

• further from the principal axis, so the image will be smaller than the object

What does this diagram show?

ray diagram for an object viewed through a concave lens