The Law of Reflection and Lasers

In summary: Yes, this could happen. But to perceive a red dot you don't necessarily need more red than blue light coming from that dot. It might be sufficient to have more red light from the dot, than from the surrounding surface. Our brain calibrates our color perception based on background and ambient light.
  • #1
joejoe1234
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So I've been looking into the Law of Reflection with Specular and Diffuse Reflection. I understand that electrons have a certain vibrational frequency in objects, and if a light wave matches that, that color wouldn't be observed.

My question is, what if I took a red laser pointer and shined it at that same object? If it wasn't red in the first place, shouldn't it technically also absorb that red color? I know it's not the case, cause obviously we see that red dot. Does that red laser pointer follow the law of reflection?
 
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  • #2
The law of reflection

http://www.colormatters.com/color-and-vision/how-the-eye-sees-color

So sunlight has all the colors and the apple absorbs them except for red and so the red is reflected.

When you shine a red laser on the apple, it simply reflects the red and so you see the red laser dot. The reason you see the dot on a red object is because it may not absorb that specific frequency of red as found in the red laser.
 
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  • #3
So let's say I have a blue object, which by definition absorbs all wavelengths except blue. If I shine a red laser on it, I still see the red dot. Shouldn't it be absorbing that red wavelength though?
 
  • #4
joejoe1234 said:
So let's say I have a blue object, which by definition absorbs all wavelengths except blue.
That would require a perfectly blue object.

joejoe1234 said:
If I shine a red laser on it, I still see the red dot.
Then it's not a perfectly blue object.
 
  • #5
A.T. said:
That would require a perfectly blue object.Then it's not a perfectly blue object.

I think I'm starting to get it. How come though the "not perfectly blue" object only reflects the red light of the red laser pointer but not the sun?
 
  • #6
joejoe1234 said:
How come though the "not perfectly blue" object only reflects the red light of the red laser pointer but not the sun?
It does reflect some of the sun's red light, but much more blue light, so it appears blue.
 
  • #7
A.T. said:
It does reflect some of the sun's red light, but much more blue light, so it appears blue.
So when you shine a red laser on it, more red is reflected than blue, so you see a red dot?
 
  • #8
joejoe1234 said:
So when you shine a red laser on it, more red is reflected than blue, so you see a red dot?
Yes, this could happen. But to perceive a red dot you don't necessarily need more red than blue light coming from that dot. It might be sufficient to have more red light from the dot, than from the surrounding surface. Our brain calibrates our color perception based on background and ambient light.
 

1. What is the Law of Reflection?

The Law of Reflection states that when a light ray hits a smooth surface, the angle of incidence (the angle at which the light ray hits the surface) is equal to the angle of reflection (the angle at which the light ray bounces off the surface).

2. How does the Law of Reflection apply to lasers?

The Law of Reflection applies to lasers in the same way it applies to any other light source. When a laser beam hits a smooth surface, it will reflect off the surface at the same angle it hit the surface, creating a predictable path for the laser beam.

3. Can the Law of Reflection be broken or altered?

No, the Law of Reflection is a fundamental law of physics and cannot be broken or altered. It applies to all types of light, including laser light, and is a crucial principle in understanding how light behaves.

4. How is the Law of Reflection used in everyday life?

The Law of Reflection is used in many everyday applications, such as mirrors, glasses, and other reflective surfaces. It is also used in optical devices, such as telescopes and cameras, to manipulate and control the path of light.

5. Are there any exceptions to the Law of Reflection?

There are a few exceptions to the Law of Reflection, such as when light hits a rough or irregular surface, it may scatter in different directions rather than reflecting at a predictable angle. In this case, the law still applies, but the surface may cause the light to scatter in different directions.

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