The document discusses reflection of light, including specular and diffuse reflection. It defines the law of reflection, which states that the angle of incidence equals the angle of reflection, and that the incident ray, reflected ray, and normal ray all lie in the same plane. Specular reflection occurs off smooth surfaces, reflecting light in one direction, while diffuse reflection occurs off rough surfaces, scattering light in many directions. The document uses examples and diagrams to illustrate these concepts.

1. REFLECTI
ON
Ida Lyn A. Azuelo BSED Physics 3

2. • involves two rays
• Specular and Diffuse
• “Law of Reflection”
REFLECTION

3. LAW OF REFLECTION
 When light falls on a
surface which is plane,
the angle with which the
light falls on the surface
is equal to the angle
with which the light
reflects back and the
incident ray, reflected
ray and the normal ray
lies in the same plane.

4. Reflection
 All the light travelling
in one direction and
reflecting from the
mirror is reflected in
one direction.
 Smooth, shiny
surfaces
 The rays incident at
slightly different
points on the
surface are reflected
in completely
different directions.
 Rough, dull surfaces
Specular Reflection Diffuse Reflection

5. Specular Reflection

6. Specular Reflection
 Which part of the figures (a) or (b), better
shows specular reflection of light from the
roadway?

7. Diffuse Reflection

8. Applying Physics
 An observer on the west-facing beach of a
large lake is watching the beginning of a
sunset. The water is very smooth except for
some areas with small ripples. The observer
notices that some areas of the water are blue
and some are pink. Why does the water
appear to be different colors in different areas?

9. Explanation
 The different colors arise from specular and
diffuse reflection. The smooth areas of the
water will specularly reflect the light from the
west, which is the pink light from the sunset.
The areas with small ripples will reflect the
light diffusely, so light from all parts of the sky
will be reflected into the observer’s eyes.
Because most of the sky is still blue at the
beginning of the sunset, these areas will
appear to be blue.

10. The light reflects off in all directions because of the
irregularities on the surface of an object that are
larger than the wavelength of light but it does not
mean that the law of reflected is flouted. All objects
obey the law of reflection on a microscopic level. This
means that at different points on the surface, the
normal is different. The angle of reflection is still
equal to the angle of incidence at that point and the
normal is unique at that point in the surface.
NAIVE CONCEPTION (corrected
version)

11. Test. 
1.
Specula
r or
Diffuse
Reflectio
n?
Plane mirror

12. Test. 
1.
Specula
r or
Diffuse
Reflectio
n?

13. Keep in mind that the diagrams are made to view
in a microscopic outlook of an object on the atomic
level. There are billions of light rays and billions of
surfaces. So while seeing things, a lot of the light is
diffused. That's why when a person looks at
something, even if it is not directly faced into the
sun, the person still get enough light to see it.
NAIVE CONCEPTION (corrected
version)
In diffused reflection light scatters away then
people must not be able to see it. So, how are
people seeing any things in the world?

14. References
 (1999, July 27). Retrieved December 6, 2014, from The reflection and refraction of
light: http://physics.bu.edu/~duffy/PY106/Reflection.html
 Doris Jeanne Wagner and Rensselaer Polytechnic Institute. (2004). Retrieved
December 6, 2014, from Sample Problems for The Law of Reflection:
http://www.rpi.edu/dept/phys/ScIT/InformationTransfer/reflrefr/rr_sample/rrsample_05
.html
 Elert, G. (2010). Reflection. Retrieved December 6, 2014, from The Physics
Hypertextbook: http://physics.info/reflection/
 Fitzpatrick, R. (2007, July 7). Law of Reflection. Retrieved December 6, 2014, from
http://farside.ph.utexas.edu/teaching/302l/lectures/node127.html
 Freudenrich, P. C. (2001, March 6). How Fiber Optics Work. Retrieved December 6,
2014, from HowStuffWorks.com: http://computer.howstuffworks.com/fiber-optic.htm
 Geometric Optics. (2014). Retrieved December 6, 2014, from SparkNotes:
http://www.sparknotes.com/physics/optics/geom/problems.html

15. References
 Law of Reflection. (2014). Retrieved December 6, 2014, from TutorVista.com:
http://physics.tutorvista.com/light/law-of-reflection.html
 Lesson 26: Reflection & Mirror Diagrams. (2013, July 11). Retrieved December 6,
2014, from studyphysics.ca:
http://www.studyphysics.ca/2007/30/07_emr/26_reflection_mirror.pdf
 Optics 4 Kids. (2014). Retrieved December 6, 2014, from The Reflection of Light:
http://www.optics4kids.org/home/content/what-is-optics/reflection/the-reflection-of-
light.html
 Serway, R. A., & Jewett, J. W. (2014). Physics for Scientists and Engineers with
Modern Physics Ninth Edition. Boston: Brooks/Cole.
 Serway, R. A., Vuille, C., & Faughn, J. S. (2009). College Physics Eighth Edition.
California: Brooks Cole.
 Specular and diffuse reflection 2. (2014, May 8). Retrieved December 6, 2014, from
Khan Academy : https://www.khanacademy.org/test-prep/mcat/physical-
processes/reflection-and-refraction/v/specular-and-diffues-reflection

16. References
 The Law of Reflection. (1996-2014). Retrieved December 6, 2014, from the Physics
Classroom: http://www.physicsclassroom.com/Class/refln/u13l1c.cfm
 Total Internal Reflection. (2010, December 9). Retrieved December 6, 2014, from
Youtube: Khan Academy: https://www.youtube.com/watch?v=WRuatAcd2WY
 Total internal reflection. (2014, May 8). Retrieved December 6, 2014, from Khan
Academy: https://www.khanacademy.org/test-prep/mcat/physical-
processes/reflection-and-refraction/v/total-internal-reflection
 Weisstein, E. W. (2007). Law of Reflection. Retrieved December 6, 2014, from Eric
Weisstein's World of Physics:
http://scienceworld.wolfram.com/physics/LawofReflection.html

18. REFLECTI
ON
Ida Lyn A. Azuelo BSED Physics 3