Question

A real image is formed by a convex lens on the screen. If half of the lens is covered by an opaque object, then

• A. half image is not seen
• B. full image of same intensity is seen
• C. half image of same intensity is seen
• D. full image of decreased intensity is seen

Hint:

Every part of a lens forms the whole image. Less lens area only means less light.

Answer 1

The Correct Option is D

Step 1: Think in Rays:
Draw many rays from one point of the object. They cover the whole lens. Each ray that reaches the lens bends and meets the other rays at one image point.

Step 2: Effect of the Cover:
Covering half the lens stops the rays that hit that half. The rays that hit the open half still meet at the same image point. This is true for every object point, so no part of the image is missing.

Step 3: Brightness:
Brightness depends on how much light energy reaches the screen. Half the lens area collects about half the light. So the image has about half the intensity of before.

Step 4: Match with Options:
The image is complete and dimmer. That is option 4.

Final Answer:
\[\boxed{\text{Option 4: full image, decreased intensity}}\]