A projector has an arrangement of lenses as shown in the figure below. A bulb il

Question

A projector has an arrangement of lenses as shown in the figure below.

A bulb illuminates an object and the light then passes through a lens that creates an

image on a distant screen, as shown. When a piece of cardboard is brought up to

cover the lower half of the lens, which of the following happens to the image on the

screen?

a. The top half of the image disappears.

b. The bottom half of the image disappears.

c. The image remains, but is weaker (not as bright).

d. The image remains unchanged.

e. The bottom half of the image becomes weaker; the top is unchanged.

f. The top half of the image becomes weaker; the bottom is unchanged.

g. Something else happens (tell what it is).

Explain your reasoning, drawing whatever rays are needed to make your point clear.

Explanation / Answer

A bulb illuminates an object and the light then passes through a lens that creates an image on a distant screen, as shown. When a piece of cardboard is brought up to cover the lower half of the lens, which of the following happens to the image on the screen?

The top half of the image disappears.

The bottom half of the image disappears.

The image remains, but is weaker (not as bright).

The image remains unchanged.

The bottom half of the image becomes weaker; the top is unchanged.

The top half of the image becomes weaker; the bottom is unchanged.

Something else happens (tell what it is).

Explain your reasoning, drawing whatever rays are needed to make your point clear.
The image remains, but is weaker (c). Light can still go from the object, through the lens, and to all parts of the image on the screen. However, since part of the lens is blocked, less total light can get through, making the image weaker.

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