Class 10 Science

# Reflection by Spherical Mirror

These notes are based on the chapter Light: Reflection and Refraction from class 10 science NCERT book and CBSE syllabus

• Incident ray parallel to principal axis
• Incident ray passing through C
• Incident ray passing through F
• Incident ray passing obliquely through principal axis

When a ray of light is reflected by a spherical mirror, there are many possibilities of behaviour by reflected ray. The path of reflected ray depends on the point of incidence on the given spherical mirror.

The incident ray can be parallel to the principal axis, it may pass through C or through F. The reflected ray behaves differently in different situations.

## Reflection of Rays parallel to Principal Axis

In the case of concave mirror: A Ray parallel to principal axis passes through the principal focus after reflection from a concave mirror.

Fig: Rays parallel to principal axis

Similarly, all parallel rays to the principal axis pass through the principal focus after reflection from a concave mirror. Since, a concave mirror converge the parallel rays after reflection, thus a concave mirror is also known as converging mirror.

In the case of convex mirror: A ray parallel to principal axis appears to diverge from the principal focus after reflecting from the surface of a convex mirror.

Fig: Rays parallel to principal axis

Similarly, all rays parallel to the principal axis of a convex mirror appear to diverge or coming from principal focus after reflection from a convex mirror. Since, a convex mirror diverges the parallel rays after reflection, thus it is also known as diverging mirror.

## Reflection of ray passing through the Principal Focus:

In the case of concave mirror: Ray passing through the principal focus goes parallel to principal axis after reflection in the case of concave mirror.

Fig: Ray passing through principal focus

In the case of convex mirror: A ray directed towards principal focus goes parallel to principal axis after reflecting from the surface of a convex mirror.

Fig: Ray through principal focus

## Ray passing through the Centre of curvature:

In the case of concave mirror: Ray passing through the centre of curvature returns at the same path after reflecting from the surface of a concave mirror.

Fig: Ray passing through C

In the case of convex mirror: Ray appears to passing through or directed towards the centre of curvature goes parallel to the principal axis after reflecting from the surface of a convex mirror.

Fig: Ray passing through C

## Ray incident obliquely to the principal axis

Ray obliquely to the principal axis goes obliquely after reflecting from the pole of the both concave and convex mirror and at the same angle.

Fig: Ray passing obliquely to principal axis

More from this Lesson