Question

In projectors _______ lenses are used

• A. Convex
• B. Concave
• C. Bipolar
• D. Convex lens and Concave

Hint:

Projectors use convex lenses because convex lenses can form real and magnified images on a screen.

Answer 1

The Correct Option is A

Concept:
A projector is an optical device used to form a magnified image on a screen. For forming a real and enlarged image on a screen, a convex lens is used. A convex lens is a converging lens.

Step 1: Understand what a projector does.
A projector takes a small object or image and projects a larger image on a screen. The image formed on the screen must be: \[ \text{real} \] \[ \text{magnified} \] Only a convex lens can form a real magnified image under suitable object position.

Step 2: Recall image formation by convex lens.
A convex lens forms a real and enlarged image when the object is placed between: \[ F \text{ and } 2F \] The image is formed beyond \(2F\), and it can be obtained on a screen.

Step 3: Why concave lens is not used.
A concave lens is a diverging lens. It generally forms: \[ \text{virtual} \] \[ \text{erect} \] \[ \text{diminished} \] images. So it is not suitable for ordinary projectors.

Step 4: Check the options.
Option (A) Convex is correct.
Option (B) Concave is incorrect.
Option (C) Bipolar is not the correct lens type here.
Option (D) Convex lens and Concave is not the standard answer. Hence, the correct answer is: \[ \boxed{(A)\ \text{Convex}} \]