Physics · Light
Convex and Concave Lenses: Ray Diagrams
A lens bends light to form an image. Where the image forms and what it looks like depends on where the object is.
- Object distance u
- −30 cm
- Focal length f
- +10 cm
- Image distance v
- 15 cm
- Magnification m = v/u
- -0.5
- Image
- Real, inverted, diminished
Lens
Try this
- Convex lens: put the object at 2F. Where is the image?
- Move it between F and the lens. What kind of image do you get?
- Concave lens: can you ever get a real image?
Key ideas
- Lens formula: 1/v − 1/u = 1/f (NCERT sign convention).
- Magnification m = v/u; negative m means inverted.
- A concave lens always gives a virtual, erect, diminished image.