Is a Two-Sided Reflective Dish Considered a Hologram?

[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.