An object is 30 cm before a concave mirror of focal length 15 cm. Find image position.
Answer framework: Use u = −30 cm, f = −15 cm in mirror formula; report v = −30 cm and real, inverted, same-size image.
All Class 10 Science notes
Chapter 9 • Physics
Light – Reflection and Refraction
Apply sign conventions, ray diagrams, mirror and lens formulae, magnification and refractive index to image formation.
Core concepts checklist
Laws of reflection and spherical mirrors
Ray diagrams for concave and convex mirrors
Refraction and refractive index
Ray diagrams for convex and concave lenses
Power of a lens and numerical problem solving
Formula & fact bank
1/f = 1/v + 1/u
Mirror magnification: m = hᵢ/hₒ = −v/u
n = c/v
Lens magnification: m = hᵢ/hₒ = v/u
P = 1/f(m), unit dioptre
Diagrams to practise
Draw with pencil, use straight label lines, add arrows and write a precise caption.
- 1Six concave-mirror cases
- 2Convex-mirror image
- 3Six convex-lens cases
- 4Concave-lens image
CBSE examiner focus
- Write the Cartesian sign convention before substitution
- Draw two standard rays with arrows
- Include unit and nature/position/size of image in numerical conclusions
Board-style practice
Draw and explain image formation by a convex lens for three object positions.
Answer framework: Choose beyond 2F, at 2F and between F–2F; label rays, image nature, size and position.
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