Basic doubt about a concept in Optics

In summary, a plane mirror and a white sheet of paper both reflect all wavelengths of light incident on them. However, white paper does not produce a clear reflection like a mirror because of its irregularities and diffuse reflection properties. This is due to the material itself and not just the smoothness of the surface. Additionally, the term "white" means that all parts of the spectrum are reflected equally, but some light may still be absorbed by the surface.
  • #1
ShreyasR
88
2
This may sound really silly but yeah, a plane mirror, and a white sheet of paper, both reflect all the wavelengths of light incident on them. So Instead of a plane mirror, if I use a white sheet of paper, Why don't I see a reflection of myself?
I have studied ray diagrams, and i know how an image is formed by a plane mirror (which can be explained by ray diagrams). If a white sheet of paper can reflect all light, why can't I draw the same ray diagram with a white paper instead of a mirror?
 
Science news on Phys.org
  • #2
Maybe, because of the irregularities present on the surface of the paper, the reflected rays are not parallel... so we don't obtain any sharp image as such... the rays get dispersed.
 
  • #3
But what about smooth, laminated papers?
 
  • #4
ShreyasR said:
This may sound really silly but yeah, a plane mirror, and a white sheet of paper, both reflect all the wavelengths of light incident on them. So Instead of a plane mirror, if I use a white sheet of paper, Why don't I see a reflection of myself?
I have studied ray diagrams, and i know how an image is formed by a plane mirror (which can be explained by ray diagrams). If a white sheet of paper can reflect all light, why can't I draw the same ray diagram with a white paper instead of a mirror?

This is because of diffuse reflection; see these links:

Specular vs. Diffuse Reflection
Diffuse reflection (wiki)

and you will see that it's not only the smoothness of the surface that plays a role - it's also the material itself. I'm pretty sure the material thickness also has some role.
 
Last edited:
  • Like
Likes 1 person
  • #5
DennisN said:
This is because of diffuse reflection; see these links:

Specular vs. Diffuse Reflection
Diffuse reflection (wiki)

and you will see that it's not only the smoothness of the surface that plays a role - it's also the material itself. I'm pretty sure the material thickness also has some role.

Thank you :-) And when we say that a white object appears white because it reflects all the wavelengths incident on it, does it mean that the intensity of the reflected light is proportional to the incident light or it need not meet this condition? (for white light)
 
  • #6
The term "white" typically means that all parts of the spectrum are reflected equally.

Claude.
 
  • Like
Likes 1 person
  • #7
Claude Bile said:
The term "white" typically means that all parts of the spectrum are reflected equally.

Claude.
And some of the light may get absorbed by the white surface. As Claude said, White means that all parts of the spectrum are reflected equally. That means the intensity need not be same as the incident light intensity.
 
  • Like
Likes 1 person
  • #8
ShreyasR said:
But what about smooth, laminated papers?

I think the lamination is what is smooth - and it's clear (non-reflective). The paper below is still bumpy and had diffuse reflections.
 
  • Like
Likes 1 person

Related to Basic doubt about a concept in Optics

1. What is the difference between reflection and refraction?

Reflection occurs when light bounces off a surface, while refraction is the bending of light as it passes through a medium. Reflection follows the law of reflection, where the angle of incidence is equal to the angle of reflection, while refraction follows Snell's law, where the angle of incidence and the refracted angle are related by the indices of refraction of the two mediums.

2. How does a lens work?

A lens works by refracting (bending) light as it passes through, causing the light rays to converge or diverge. This is due to the varying thickness and curvature of the lens. Convex lenses, which are thicker in the middle and thinner at the edges, cause light rays to converge and can produce images. Concave lenses, which are thinner in the middle and thicker at the edges, cause light rays to diverge and can be used to correct vision in glasses.

3. What is the difference between a real image and a virtual image?

A real image is formed when light rays actually converge at a point, allowing the image to be projected onto a screen. This type of image can be seen without the use of any additional equipment. On the other hand, a virtual image is formed when the light rays only appear to converge at a point, and the image cannot be projected onto a screen. Virtual images can only be seen with the use of a mirror or lens.

4. What is the relationship between wavelength and frequency?

Wavelength and frequency are inversely proportional to each other. This means that as the wavelength increases, the frequency decreases, and vice versa. This relationship is described by the equation c = λf, where c is the speed of light, λ is the wavelength, and f is the frequency. This relationship is important in understanding the nature of light and how it behaves.

5. How does light travel through different mediums?

When light travels through a medium, it interacts with the atoms and molecules of that medium. The speed of light in a medium is determined by the optical density of the medium, which is related to the refractive index. As the light passes through the medium, it may be absorbed or scattered by the atoms and molecules, which can affect the overall intensity and direction of the light. The refractive index of a medium also determines the angle at which light will be refracted, as described by Snell's law.

Similar threads

I Applications of Virtual objects
    • Optics
Replies
9
Views
2K
I Image appears outside of q -- Lens Maker's Equation confusion
    • Optics
Replies
17
Views
2K
Optics question: Looking at mirrors from parallel to the surface
    • Optics
Replies
6
Views
885
Virtual and real image with concave mirror at 45 degrees
    • Optics
Replies
4
Views
1K
I Doubts about Fourier transform of IR spectroscopy
    • Optics
Replies
3
Views
1K
Drop in intensity when light is focused to a point (telescope mirror)
    • Optics
Replies
8
Views
1K
Ray Diagram for an Experimental Lens Systems
    • Optics
Replies
17
Views
1K
Ray Optics Doubt: Can an Equilateral Triangle Form?
    • Optics
Replies
11
Views
1K
Why do eyes only see in straight lines? (Light Physics)
    • Optics
Replies
4
Views
4K
Concave mirror: Reflected rays do not meet at one point
    • Optics
Replies
12
Views
2K

Hot Threads

Recent Insights

Back
Top