Physics Review Question
Unit: Waves
Year: 1992 Question#: 41
Question: When light rays from an object are incident upon
an opaque rough textured suface, no reflected image of the object can be
seen. This phenomenom occurs because of
(1 ) regular reflection
(2 ) diffuse reflection
(3 ) reflected angles not being equal to
incident angles
(4 ) reflected angles not being equal to
refracted angles
What is this question really asking?
Explanation by: Lindsay K
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Answer 1
1) regular reflection
Incorrect
Regular reflection deals with parrallel light rays striking aSMOOTH PLANE
SURFACE, and reflecting also as parrallel light rays because the normals
to the surface all point in the same direction. Regular reflection has nothing
to do with rough textured surfaces. 
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Answer 2
diffuse reflection
CORRECT
Diffuse reflection is the correct choice because diffuse reflection is when
parrallel light rays strike a ROUGH TEXTURED SURFACE, and because of the
uneven surface the reflected rays are scattered in all directions. Though
each individual light ray obeys the law of reflection the uneven surface
makes the normals not parrallel, so reflected light rays aren't parrallel,
then the object can't be seen because the image is not formed.
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Answer 3
3) reflected angles not being equal to incident angles
INCORRECT
Each individual light ray that strikes the uneven textured surface will
obey the Law of Reflection, despite the surface irregularities; and the
Law of Reflection says that reflected angles WILL BE EQUAL to incident angles
in respect to the normal. 
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Answer 4
reflected angles not being equal to refracted angles
INCORRECT
Notice the object is opaque, that means that light won't be refracted, so
you can eliminate choice 4 because it's talking about refraction. return to top
What's this question really asking?
What happens to light rays that strike opaque uneven textured surfaces and
what is diffuse reflection
