A luminous toy was placed in front of a converging lens.Suppose the bottom half of the lens is covered with cardboard.State the effect this change would have on the brightness and size of the image...

A luminous toy was placed in front of a converging lens.Suppose the bottom half of the lens is covered with cardboard.State the effect this change would have on the brightness and size of the image formed on the screen.Thanks

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justaguide | College Teacher | (Level 2) Distinguished Educator

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A luminous toy is placed in front of a converging lens. Now the bottom half of the lens is covered with cardboard. The affect of doing this on the image is that the brightness of the image decreases by half.

It should be noted that the size of the image is not changed. If half the lens is blocked out it does not result in the formation of an image of only half of the object. The image formed is that of the complete object. But as only half the light passes through the lens the brightness of the image is half that of the original image.

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