- The normal point on a mirror is reflected perpendicularly
- For a light ray reflected by a mirror :
Angle of incidence = angle of reflection
☞The principal focus on a concave mirror is the point where parallel rays are focused to by the mirror.
☞A concave mirror forms:
- A real inverted image if the object is beyond the principal focus of the mirror.
- A enlarged,upright virtual image if the object is between the mirror and the principal focus.
☞A convex mirror always forms a virtual image of an object.
A concave mirror when the object is place beyond the point of curvature. The image formed is real and inverted.
A concave mirror when the object is placed betweenthe mirror and the focal point. The image formed in enlarged, upright andvirtual.
Refraction of light is the change of direction of a light ray when it crosses a boundary between two transparent substances.
If the speed is reduced, refraction is towards the normal (e.g. air to glass).
If the speed is increased, refraction is away from the normal (e.g. glass to air).
Example on refraction-Lenses👓
- A real image is formed by a converging lens if the object is further away from the principal focus.
- A virtual image is formed by a diverging lens and by a converging lens if the object is nearerthan the principal focus.
1.A converging lens
- The principle ray is parallel to the axis and is refracted through f.
- The central ray passes straight through the centre of the lens.
- The focal ray passes through f and is refracted parallel to the axis.
2.A diverging lens
The image is upright, virtualand smaller than the object.
That's the end of reflection and refraction
Drafted by Yoko Mak(Physics）