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Question Video: Identifying the Position of the Retina Science

Which of the following is the position of the retina in the eye? [A] At the front of the eye [B] At the back of the eye [C] At the center of the eye

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Video Transcript

Which of the following is the position of the retina in the eye? (A) At the front of the eye, (B) at the back of the eye, (C) at the center of the eye.

This question is asking us about the basic structure of the eye. It is asking about three different locations of the eye: the front, back, and center. We only see an object if light coming from it enters the eye and is focused on the retina. This is because the retina is the part of the eye that is sensitive to light. When light is focused, it converges, or meets, at a point. To focus light coming from objects, the eye contains a lens. A lens will focus light so that it converges to a point.

If an object is nearby, then the light from it diverges. This means the light rays are moving away from each other. If the object is far away, then the light from it is parallel. This means that the light rays are not moving farther apart nor are they moving closer together. We need to decide where both the retina and the lens need to be so that light will converge at a point on the retina.

If the retina is at the front of the eye, then the lens must be either at the back or center of the eye. For a lens at the back or center of the eye, in both cases, the light from the nearby object will not be focused onto the retina. The light rays are diverging, moving farther apart, and so will not meet at a point on the retina. This means we could not see the nearby object. Equally, light from the distant object will not be focused onto the retina. The light rays are parallel; they are not moving farther apart or moving closer together and so will not meet at a point on the retina. This means we could not see the distant object either. So, the correct answer cannot be option (A).

We require the lens to be at the front of the eye. When the lens is at the front of the eye, we can draw a correct ray diagram, showing the path of the light rays from both objects as they enter the eye through the lens. If the retina is located in the center of the eye, then the light from both the nearby and the distant objects would not focus at a point on the retina. We only see an object if light coming from the object is focused on the retina. So, the retina cannot be in the center of the eye. Hence, option (C) cannot be the correct answer.

If the retina is located at the back of the eye, then the light from both the nearby and the distant objects focuses at a point on the retina. This means we can see both objects. Hence, option (B) is the correct answer. The retina is located at the back of the eye.

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