# Lenses can produce real and virtual images

• A real image is where the light from an object comes together to form an image on a screen-like the image formed on an eye’s retina

• A virtual image is where the rays are diverging, so the light from the object appears to be coming from a completely different place

• When you look in a mirror you see a virtual image of your face- because the object appears to be behind the mirror

• You can get a virtual image when looking at an object through a magnifying lens-the virtual image looks bigger than the object actually is

To describe an image you need to say: how big it is compared to the object, whether it’s upright or inverted relative to the object, whether its real or virtual

# Draw a ray diagram from an image through a convex lens

• Pick a point on the top of the object. Draw a rau going from the object to the lens parallel to the axis of the lens

• Draw another ray from the top of the object going right through the middle of the lens

• The incident ray that’s parallel to the axis is refracted through the principal focus on the other side of the lens. Draw a refracted ray passing through the principal focus

• The ray passing through the middle of the lens doesn’t bend

• Mark where the rays meet. That’s the top of the image

• Repeat the process for s point on the bottom of the object. When the bottom of the object is on the axis, the bottom of the image is also on the axis

# Distance from the lens affects the image

• An object at 2F will produce a real, inverted image the same size as the object, and at 2F

• Between F and 2F it’ll make a real, inverted image bigger than the object, and beyond 2F

• An object nearer than F will make a virtual image the right way up, bigger than the object, on the same side of the lens