Lens and mirror calculator
Pick a lens or mirror, give its focal length and the object distance, and get where the image forms, its magnification and nature - with the New Cartesian sign convention, the working and the ray diagram.
Answer
- Image distance v
- 12 cm
- Magnification m
- 0.4
- Image is
- diminished, erect, virtual
Ray diagram
Working
- Sign convention: distances are measured from the mirror, positive in the direction the light travels (towards the mirror); so u = -30 cm and f = 20 cm.
- 1/v + 1/u = 1/f: 1/v = 1/f - 1/u = 1/(20) - 1/(-30), so v = 12 cm.
- m = -v/u = 0.4; image height = m × object height = 0.4 cm.
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