This presentation is one of the series as part of the Australian Curriculum for Year 9 Science students. It covers the Physical Sciences (PS) strand of Science Understanding. 9 PS Light II AO covers the theme of 'Energy transfer through different mediums can be explained using wave and particle models (ACSSU182)'. The elaboration is exploring the properties of waves, and situations where energy is transferred in the form of waves, such as sound and light. Light II covers the Law of Reflection.

4. The incident ray, the reflected ray and the normal
line all line in the same plane.
PLANE MIRROR
Ray of
incidence
Ray of
reflection
Normal line

5. The incident ray or ray of incidence refers to the
light ray that is directed towards the plane mirror.
PLANE MIRROR
Ray of
incidence

6. The normal line refers to an imaginary line that is
perpendicular to the plane mirror.
PLANE MIRROR
Normal line

7. The reflection ray or ray of reflection refers to the
ray that is directed away from the plane mirror.
PLANE MIRROR
Ray of
reflection

8. PLANE MIRROR
Angle of incidence = angle of reflection
i° = r°
i° r°

9. PLANE MIRROR
The angle of incident (i°) is the angle between the
normal line and the ray of incidence.
i°

10. PLANE MIRROR
r°
The angle of reflection (r°) is the angle between the
normal line and the ray of reflection.

11. Smooth surfaces like the calm water
allows light to be reflected evenly.
This is known as a specular reflection.

12. Rough surfaces like the rippled and paddled
water allows light to be reflected unevenly.
This is known as a diffuse reflection.

13. The figure shows a light ray striking a surface of a plane mirror at an angle
of 50°.
50°
(a) Determine the angle of
incidence.
(b) Complete the ray of
reflection.

14. The figure shows a light ray striking a surface of a plane mirror at an angle
of 50°.
50°
(a) Determine the angle of
incidence.
ANSWER
The angle of incidence is between
the ray of incidence and the
normal line.
The normal line is perpendicular
to the plane mirror.
90° – 50° = 40°
40°
Normal line

15. The figure shows a light ray striking a surface of a plane mirror at an angle
of 50°.
50°
(b) Draw the ray of reflection.
40° 40°
ANSWER
i = 40°
i = r = 40°
Ray of reflection is drawn away
from the normal.

16. Complete the diagram by sketching reflected rays for an uneven surface.

17. Complete the diagram by sketching reflected rays for an uneven surface.
ANSWER
The reflected rays of the incident rays are drawn randomly but the ray is
still a straight line.

18. Real
Object
Virtual
Image
Rays of light do not meet
to produce the image.

19. 3. Upright (normal way up).
1. Same size as the object.
2. Virtual.

20. 4. Appears located far
inside the mirror as
objects are in front.
5. Lateral inversion
(reverses left and
right).