Ray Optics And Optical Instruments

Let's analyze the two statements:

1. Statement (a): "Virtual image can be seen with the eyes." A virtual image is formed when the rays of light appear to diverge from a point, such as the image seen in a flat mirror. Unlike real images, virtual images cannot be projected onto a screen, but they are visible to the observer. Therefore, this statement is true.
2. Statement (b): "Virtual image can be captured on the screen." A virtual image cannot be projected on a screen because the light rays do not converge in physical space. They only appear to do so when extended backward. Hence, this statement is false.

Based on the analysis, only statement (a) is true. Therefore, the correct option is: Only (a) is true

A lens is a transparent medium bounded by two surfaces, both of which can be curved or one can be curved while the other is flat. The nature of the lens is determined by the curvature of these bounding surfaces.

In this case, the question describes a lens with two spherical surfaces curved inwards. These inwardly curved surfaces indicate that the lens is concave on both sides. Such a lens is known as a "biconcave" lens.

The properties of biconcave lenses include:

• They diverge light rays that pass through them.
• They are typically used in applications where light needs to be spread out, such as in eyeglasses for nearsightedness.
• The focal length of the biconcave lens is negative, indicating its diverging nature.

Therefore, the correct answer is: biconcave