Which of the following curved surfaces will produce a real image? I. Concave mirror II. Convex mirror III. Diverging lens IV. Converging lens

Analyze the question: You are asked which of the four devices can form a real image. A real image is one where light rays actually meet (converge) at a point, so the image can be projected onto a screen.

Concept:

• Concave mirror is a converging mirror. When the object is beyond the focal length, it forms a real, inverted image. (When the object is inside the focal length, the image is virtual.)
• Convex mirror is a diverging mirror. It always forms a virtual, erect, diminished image.
• Diverging (concave) lens spreads light out. It always forms a virtual, erect, diminished image.
• Converging (convex) lens converges light. When the object is beyond the focal length, it forms a real, inverted image. This is how a projector or a camera works.

Solution:

• I. Concave mirror: can produce a real image ✔
• II. Convex mirror: virtual only ✘
• III. Diverging lens: virtual only ✘
• IV. Converging lens: can produce a real image ✔

So the devices that can produce a real image are I and IV only.

Checking the options:

• A (I and III): III is wrong.
• B (I, II and IV): II is wrong.
• C (II, III and V): there is no item V, and II and III are wrong.
• D (I and IV only): correct ✔

Tip: Remember that "converging" devices (concave mirror, convex lens) can form real images, while "diverging" devices (convex mirror, concave lens) only form virtual images. A quick way to remember it: only converging devices make real images.