Question

Which of the following are able to produce a virtual image? I. Convex lens II. Concave lens III. Plane mirror (A) I only (B) III only (C) II and III only (D) Il and III only

Short answer

(C) II and III only

Step-by-step solution

- Understanding Virtual Images

A virtual image is formed when the light rays appear to diverge from a point after reflection or refraction. Virtual images cannot be projected on a screen as they are formed by the apparent divergence of rays.

- Analyzing Convex Lens

A convex lens, also known as a converging lens, typically produces real images by converging light rays. However, it can produce a virtual image if the object is placed between the focal point and the lens.

- Analyzing Concave Lens

A concave lens, or a diverging lens, always produces a virtual image. The light rays diverge, and the image appears to be on the same side of the lens as the object.

- Analyzing Plane Mirror

A plane mirror always produces a virtual image. The image appears to be behind the mirror, where the reflected rays appear to diverge.

- Final Answer

From the analysis, both a concave lens and a plane mirror can produce virtual images. Hence, the correct option is II and III only.

Key concepts

concave lens

A concave lens is also known as a diverging lens. This type of lens is thinner in the middle and thicker at the edges. When light rays pass through a concave lens, they spread out or diverge. Because of this divergence, the light rays never actually meet on the other side of the lens. Instead, they appear to come from a point on the same side of the lens as the object.

This characteristic makes concave lenses produce virtual images. A virtual image is one that cannot be projected on a screen because the light rays only seem to come from the image point, but don't actually converge there.

For example, eyeglasses for people with myopia (nearsightedness) often use concave lenses to correct their vision by diverging incoming light rays before they enter the eye. This helps the image form on the retina, allowing for clear vision.

plane mirror

A plane mirror is a flat mirror that reflects light according to the law of reflection. This means that the angle of incidence (the angle at which incoming light hits the mirror) is equal to the angle of reflection (the angle at which light bounces off).

Plane mirrors always produce virtual images. These images appear to be behind the mirror at the same distance as the object is in front of it. However, the image is not real; the light rays don't actually converge behind the mirror. They simply appear to emanate from that point when traced back.

One interesting feature of plane mirror images is that they are laterally inverted. This means the left and right sides are swapped in the mirror image compared to the actual object. This is why text appears reversed in a mirror image.

Daily uses of plane mirrors include bathroom mirrors, car rearview mirrors, and decorative mirrors. They are crucial in providing clear virtual images for practical purposes.

convex lens

A convex lens, or a converging lens, is thicker in the middle and thinner at the edges. It bends incoming light rays toward a focal point, making them converge. By doing this, convex lenses typically produce real images, which can be projected onto a surface, like a screen.

However, a convex lens can also produce virtual images under specific conditions. If an object is placed between the lens and its focal point, the lens will diverge the rays as if they are coming from a point on the same side of the lens as the object. This results in a larger, upright virtual image.

Convex lenses are essential in numerous optical devices. Cameras use them to focus light and create clear photographs. Magnifying glasses use convex lenses to produce larger virtual images of small objects, making them easier to examine. They are also used in eyeglasses for people with hyperopia (farsightedness) to correct their vision.