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Q: Which of the following statements is/are true about the principal axis of a spherical mirror? (i) It is normal to the mirror (ii) Point of incidence always lies on the principal axis (iii) Principal focus always lies on the principal axis.
  • A. Only (ii)
  • B. Both (i) and (iii)
  • C. Both (i) and (ii)
  • D. Only (i)
Correct Answer: Option B - The principal axis of a spherical mirror is the line passing through the centre of the mirror and it is always remains, perpendicular to the surface of the mirror. In making ray diagrams all rays taken to be intersected through the principal axis, therefore point of incidence always line on the principal axis.
B. The principal axis of a spherical mirror is the line passing through the centre of the mirror and it is always remains, perpendicular to the surface of the mirror. In making ray diagrams all rays taken to be intersected through the principal axis, therefore point of incidence always line on the principal axis.

Explanations:

The principal axis of a spherical mirror is the line passing through the centre of the mirror and it is always remains, perpendicular to the surface of the mirror. In making ray diagrams all rays taken to be intersected through the principal axis, therefore point of incidence always line on the principal axis.