In a concave lens, the focal length is always: (2020)

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Question: In a concave lens, the focal length is always: (2020)

Options:

Correct Answer: Negative

Exam Year: 2020

Solution:

The focal length of a concave lens is always negative, as it diverges light rays.

In a concave lens, the focal length is always: (2020)

In a concave lens, the focal length is always: (2020)

Step 1: Understand what a concave lens is. A concave lens is thinner in the middle and thicker at the edges.
Step 2: Know that a concave lens diverges light rays. This means that when light rays pass through a concave lens, they spread out instead of converging.
Step 3: Learn about focal length. The focal length is the distance from the lens to the point where light rays appear to diverge from (the focal point).
Step 4: Remember that for concave lenses, the focal point is virtual, meaning it cannot be reached by real light rays. This is why the focal length is considered negative.
Step 5: Conclude that the focal length of a concave lens is always negative because it diverges light rays.

Focal Length of Lenses – The focal length of a lens determines how it converges or diverges light; concave lenses always have a negative focal length.