Understanding Lenses and Light Ray Behavior

The question asks about the type of lens that performs the action of collecting incoming light rays. Different types of lenses interact with light in distinct ways, causing the light rays to change direction as they pass through.

What Happens When Light Passes Through a Lens?

When parallel rays of light, such as those coming from a distant object, strike a lens, they are either brought together or spread apart. The way the lens affects these rays depends on its shape and the material it is made of.

• Collecting Rays: A lens that collects or converges parallel rays of light towards a single point (known as the principal focus) is called a converging lens.
• Spreading Rays: A lens that spreads or diverges parallel rays of light away from a single point is called a diverging lens.

Analyzing the Options

Let's look at the given options in the context of collecting light rays:

• Converging lens: This type of lens is specifically designed to bring parallel light rays together. Convex lenses are common examples of converging lenses. They are thicker in the middle than at the edges.
• Diverging lens: This type of lens spreads parallel light rays apart. Concave lenses are common examples of diverging lenses. They are thinner in the middle than at the edges.
• Plano lens: A plano lens has one flat surface. The other surface can be convex (plano-convex, which is converging) or concave (plano-concave, which is diverging). The term "plano lens" itself doesn't specify whether it collects or spreads rays without mentioning the shape of the other surface.
• Meniscus lens: A meniscus lens has one concave and one convex surface. It can be either converging or diverging depending on the relative curvature of the two surfaces. Like a plano lens, the term "meniscus lens" alone doesn't guarantee it collects rays.

Based on the definitions, the lens that explicitly collects or brings light rays together is the converging lens.

Detailed Explanation of Ray Tracing for Converging Lenses

For a converging lens, here are some key ray tracing rules:

• A ray of light parallel to the principal axis passes through the principal focus on the other side of the lens after refraction.
• A ray of light passing through the optical center of the lens goes undeviated.
• A ray of light passing through the principal focus on one side of the lens emerges parallel to the principal axis after refraction.

These rules demonstrate how parallel rays are collected at the focal point by a converging lens.

Conclusion

The lens that collects or converges the rays is known as a converging lens.

Revision Table: Lens Behavior

Additional Information on Lens Properties

Lenses are fundamental optical components used in many devices, from simple magnifying glasses to complex telescopes and cameras. Their ability to control the direction of light rays is crucial for forming images.

• Focal Length (\(\mathbf{f}\)): This is the distance between the optical center of the lens and its principal focus. For a converging lens, the focal length is positive. For a diverging lens, it is negative.
• Power of a Lens (\(\mathbf{P}\)): The power of a lens is a measure of its ability to converge or diverge light. It is defined as the reciprocal of the focal length in meters (\(P = 1/f\)). The unit of power is the dioptre (D). Converging lenses have positive power, while diverging lenses have negative power.
• Lens Maker's Formula: This formula relates the focal length of a lens to its refractive index and the radii of curvature of its surfaces:

  \( \frac{1}{f} = (n-1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \)

  where \(n\) is the refractive index of the lens material, \(R_1\) is the radius of curvature of the first surface, and \(R_2\) is the radius of curvature of the second surface. This formula helps determine the focal length based on the lens's physical properties.