Convex lenses can focus rays
A convex lens can make real images when the object is outside the focal length. Cameras use this idea.
Physics Learning Tool
Lens and Ray Optics Simulator
Move an object in front of a convex or concave lens and watch rays form real or virtual images.
Big idea: lenses bend light rays. Where the rays meet, or seem to come from, is where the image appears.
Interactive ray diagram
Choose the lens type, then change object distance, focal length, object height, or lens power. The diagram and calculations update together.
Ray guide: blue rays are real light paths. Dashed rays show backward extensions for virtual images.
Image distance60 cm right
Image typeReal image
OrientationInverted
Magnification-1.00x
Camera idea: real inverted image on a sensor
Glasses idea: lenses redirect rays before they reach the eye
Watch the focal point
Move the object across F. That crossing point is where convex lenses change from real-image behavior to magnifier behavior.
Read dashed rays carefully
Dashed lines are not light traveling backward. They are construction lines that show where a virtual image appears.
Convex
60 cm
30 cm
6 cm
+3.33 D
Signed focal length+30 cm
Lens power+3.33 D
Image height-6 cm
Ray resultRays meet
1/f = 1/do + 1/diPositive image distance means the image forms on the far side of the lens. Negative image distance means the image is virtual and appears on the object side.
m = -di/doMagnification tells whether the image is larger or smaller, upright or inverted.
What is happening?
A convex lens with the object beyond the focal point forms a real, inverted image.
Presets
What students should remember
Virtual images appear by tracing rays backward
A magnifying lens makes an upright virtual image when the object is inside the focal length.
Lens power measures bending strength
Shorter focal length means stronger lens power. Eyeglass prescriptions use diopters.