Chapter: 3 Movement in & out of Cells

Adjusting the focus

• The shape of the lens is altered , to make it bend light rays by different amounts.
• The thicker the lens, the more it bends the light rays.
• The thinner it is , the less it bend them.
• This adjustment in the shape of the lens, to focus light coming from different distances, is called accommodation .
• Figure 12.18 shows how the shape of the lens is changed.
• It is held in position by a ring of suspensory ligaments.
• The tension on the suspensory ligaments, and thus the shape of the lens , is altered by means of the ciliary muscle.
• When this muscle contracts, the suspensory ligaments are loosened.
• When it relaxes, they are pulled tight.

Ziad ahmed – IGCSE-AS-A-Level-IB Biology Teacher WhatsApp: [phone]

Ziad ahmed – IGCSE-AS-A-Level-IB Biology Teacher WhatsApp: [phone]