Convex lens imaging
Move the object to find the boundary between real and virtual images.
An object beyond the focal point forms an inverted real image; an object inside the focal point forms an upright, magnified virtual image. When the object is exactly at the focal point, the emerging rays are parallel and no image forms at a finite distance. The dashed lines are the backward extensions of the rays.
Object and image distances
Image distance plotted only within ±100 cm; the curve breaks at the focal point. Positive image distance: real image, negative: virtual image.
Think about it
As the object moves from twice the focal length toward the focal point, how does the real image change?
The real image moves farther and farther from the lens and grows larger and larger. With the object exactly at the focal point, the image recedes to infinity; once the object moves inside the focal point, the image becomes upright and virtual.
Model assumptionsIdeal thin lens · paraxial rays · fixed view · dots only indicate direction of travel · positive image distance: real image, negative: virtual image
Data log
Set the parameters and click “Record data”. Record several rows with different parameters to plot their relationship and fit a straight line; pause and record at different times to study how a reading changes with time.