Hologram Question: Exploring the Definition of a Simple Physics Demonstration

[sciboinkhobbes]

Hello everyone,

An interesting discussion has arisen within my physics department.

Would this (https://www.amazon.com/dp/B0002W3J7M/?tag=pfamazon01-20) two-sided reflective dish technically fit the definition of a hologram?

We often present this demonstration to schoolchildren, talking about how light reflects off of mirrors and discussing the focal point of the dish, but parents (and some children) are apt to ask whether it's a hologram. We want to make sure we're not leading them astray.

Thanks for any clarification!

 

[Andy Resnick]

Hello everyone,

An interesting discussion has arisen within my physics department.

Would this (https://www.amazon.com/dp/B0002W3J7M/?tag=pfamazon01-20) two-sided reflective dish technically fit the definition of a hologram?

We often present this demonstration to schoolchildren, talking about how light reflects off of mirrors and discussing the focal point of the dish, but parents (and some children) are apt to ask whether it's a hologram. We want to make sure we're not leading them astray.

Thanks for any clarification!

That has nothing to do with holography. It works on the principle of a 'virtual image':

http://www.hope.edu/csi/Activity_Kits/FloatingCoin_Background.pdf

 

[sciboinkhobbes]

Awesome, thank you! That confirms my suspicions. I'll have to let the physics freshmen know they can't tell the 10-year-olds it's a hologram any longer.

So my question is, how did this misconception arise in the first place? These optical illusion demonstrations are even marketed as "holomirrors". Does it have something to do with our conceptions of floating 3D holograms from the movies? It appears that a true hologram is much different, simply a photograph made with interference patterns from multiple light sources.

Is the confusion maybe also attributed to the idea of light interfering to produce the "floating coin" image?

And finally, are 3D holographic projections possible/have they been created (like Princess Leia... "Help me, Obi-Wan!")?

 

[Andy Resnick]

Are you asking why a company would give a meaningless spiffy sci-fi name to their product? I suspect marketing.

3D holographic projection systems have been developed in fits and spurts for the past 20 years or so- I'm not familiar with current state-of-the-art, but the systems I have seen have a very restricted view angle- your head has to be held in fairly precise alignment with the display.

 

[pmacias]

I can provide some clarification on the definition of a hologram and how it relates to this two-sided reflective dish. A hologram is a three-dimensional image created by the interference of light beams from a laser or other coherent light source. In order for an image to be considered a hologram, it must contain information about the depth, position, and intensity of the object being recorded. This means that a simple reflection off of a mirror, such as in the case of the two-sided reflective dish, would not technically be considered a hologram. Instead, the image created by the dish is a two-dimensional reflection of the object being viewed.

However, this does not mean that the dish demonstration is not valuable or educational. It can still be used to teach about the principles of reflection and focal points in a simple and engaging way. It is important to clarify to students and parents that while the dish may resemble a hologram, it is not technically one. This can help avoid any confusion and ensure accuracy in the information being presented.

In conclusion, while the two-sided reflective dish may not fit the strict definition of a hologram, it can still be a useful tool in teaching basic concepts of physics. It is important to accurately explain the difference between a reflection and a hologram to avoid any misconceptions. Thank you for bringing this discussion to our attention and I hope this helps clarify the definition of a hologram.