Question

What are the changes in ciliary muscle when nearby objects and distant objects are viewed?
A. When objects near the eyes are viewed, the ciliary muscles contract and while viewing distant objects ciliary muscles relax.
B. When objects near the eyes are viewed, the ciliary muscles relax and while viewing distant objects ciliary muscles contract.
C. Ciliary muscle is not related to the functioning of the lens and provides mechanical support only.
D. Ciliary muscles contract or relax depending on the intensity of the light and not the distance of the object.

Answer 1

Hint:Ciliary muscles help to increase the curvature of the lens when the nearby objects are seen. These muscles help to decrease the curvature of the lens when the far objects are seen.

Complete step-by-step solution:Complete step by step solution: -
When nearby objects are viewed, ciliary muscles contract and increase the curvature of the lens. When the curvature of the lens increases, then the lens thickens and makes the lens more convex. Thus, its focal length decreases.
When far objects are viewed, ciliary muscles relax and decrease the curvature of the lens. When the curvature of the lens decreases, then the lens makes the lens nearly flat. Thus, its focal length increases.
Hence, option A is correct.
Additional Information: - The internal structure of an eye has the following parts- Lens, Retina, Optic nerve, Aqueous Humour, Vitreous Humour. In these parts the lens is the part which plays the important part in viewing the objects. The lens and cornea together refract light. This light focuses on the retina.
An eye has a lens which is made of a transparent material. This material/lens is flexible enough to adjust in the response to the contraction of ciliary muscles which are designed for this purpose. These muscles are located around the lens and help the lens to change its curvature and then the focal length.

Note:- Ciliary muscles contract to increase the curvature of the lens to see the nearby objects and relax to decrease the curvature of the lens to see the far objects.