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: Understanding the Question:
A convex lens forms a real image on a screen. Half of the lens is blocked. We must say what happens to the image.

Step 2: Key Idea:
Light from every point of the object spreads out and falls on the whole face of the lens. Each part of the lens sends light from that object point to the same image point. So every part of the lens forms the complete image.

Step 3: What Blocking Half the Lens Does:
If half the lens is covered, the other half still receives light from every point of the object. It still forms the full image. But only half the light gets through, so the image is dimmer.

Step 4: Checking Each Option:
Option 1 says half the image is lost. This is wrong because the remaining half of the lens still forms the whole image.
Option 2 says the intensity stays the same. This is wrong because only half the light passes.
Option 3 is wrong for both reasons.
Option 4 says the full image is seen with less intensity. This is correct.

Final Answer:
The image stays complete but becomes dimmer, so option 4 is correct. \[ \boxed{\text{Full image of decreased intensity}} \]