Question

When object moves closer to convex lens, the image formed by it shifts :

• A. away from the lens.
• B. towards the lens.
• C. first towards and then away from the lens.
• D. first away and then towards the lens.

Hint:

For a real image in a convex lens, as the object moves closer to the lens, the image always moves away from the lens.
They move in the same absolute direction along the axis.

Answer 1

The Correct Option is A

Step 1: Recall the extreme positions first.
When the object sits at infinity, the image forms right at the focus $F_2$, which is the closest the image can ever get to the lens. When the object is brought down to the focus $F_1$ itself, the outgoing rays become parallel and the image runs off to infinity, the farthest it can possibly be.
Step 2: Notice the direction of change.
Going from the first case to the second case, the object has moved closer to the lens, while the image has moved from being right at the focus all the way out to infinity.
Step 3: Check an in-between position to be sure.
At $u = -2f$ the image sits at $v = 2f$, and as the object is brought in from $2f$ towards $f$, the image keeps sliding further away from $2f$ towards infinity, never turning back.
Step 4: State the overall trend.
So throughout the whole approach of the object towards the lens, the image consistently keeps moving away from the lens.
\[ \boxed{\text{away from the lens}} \]