Assume you are looking at the pinhole-projected image of a bright light bulb in

Question

Assume you are looking at the pinhole-projected image of a bright light bulb in a darkened room, and that the diameter of the projected image is currently D (unspecified units). If I move the projection screen twice as far away, all other things remaining the same, the diameter of the new projected image of the light bulb is how big (choose one). 0.25* 0.5*D D 2*D 4*D Going back to the original pinhole setup, if I move the lamp twice as far away, all other things remaining the same, the diameter of the new projected image of the light bulb is how big (choose one). 0.25*D 0.5*D D 2*D 4*D Going back to the original pinhole setup, you notice how bright the image of the lamp is on your projection screen, lets say the brightness is B (in unspecified units per unit area). If I move the projection screen twice as far away, all other things remaining the same, the brightness of the new projected image of the light bulb is how bright (choose one). 0.25*B 0.5*B B 2*B 4*B

Explanation / Answer

1. When the screen is moved twice as far away, then the diameter of the new projected image will be reduced by half. This will be because as the distance increases, the image formed will be reduced in size and highly focused.

0.5D

2. In this case also the projected image will be reduced in size.

0.5 D

3. In this case the brightness will be increased and image formed will be highly focussed.

2B

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