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Optics

Guest Jordan_Levy
Guest Jordan_Levy
in Other Sciences

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Why is it that when you put your finger infront of a projector's lens your finger does not cast a shadow, but if you move it away from the lens it does?

 

Further more, if your finger is infront of the lens blocking a portion of the projected image, why is it that the whole image still appears on the screen?

Why is it that when you put your finger infront of a projector's lens your finger does not cast a shadow' date=' but if you move it away from the lens it does?

 

Further more, if your finger is infront of the lens blocking a portion of the projected image, why is it that the whole image still appears on the screen?[/quote']

 

 

1. Diffraction. It's not so much that you are moving it away from the lens as you are moving it closer to the screen where the image is projected.

 

2. The rays from each point of the source map through the entire lens, not to a single point. i.e. at the lens you do not have an image

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