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14 Cards in this Set
- Front
- Back
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What are convex lenses? |
A lens refracts light and is used in many optical devices and in spectacles to form an image. A lens that bulges outwards is called a convex lens. These lenses, cause light rays to come together, or converge. If a convex lens is held close to an object, it can be used as a magnifying glass. In this case, it produces an upright and enlarged virtual image. |
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What is a real image? |
If light reaches a convex lens from a distance, the convex lens can be used to focus the light on a screen to form an image. Light is focused to a point on a screen when you see a film at the movies. This is the type of image that is formed by the convex lenses in your eyes. This type of image is called a real image. |
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What are concave lenses? |
A lens that curves inwards is called a concave lens. These lenses cause light to diverge, or spread out. They spread parallel light rays as though the rays have come from a point behind the lens. A concave lens only produces images that are smaller, upright and virtual. |
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What is the eye? |
The most incredible optical instrument we have is our eyes. Light enters the eye-refracted by the cornea and focused by the lens- convex. Incoming light is focused to form a clear, upside-down image on the retina, at the back of eye- converted into series of electrical signals. It travel along the optic nerve to the brain and it interpreted as an image. |
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What is cornea? |
A transparent covering over the iris of the eye; it bends light into the lens |
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What are lens? |
In the eye it is a flexible structure that enables light to be focused on the retina |
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What is retina? |
Nerve tissue at the back of the eye, consisting of cone cells and rod cells; light is converted into an electrical signal here |
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What is optic nerve? |
The nerve that carries messages to the brain from the retina at the back of the eye |
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What is accommodation? |
The ability of the lens of the eye to change its shape to adjust its focus. |
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What is short-sightedness (myopia)? |
The inability to focus on distant objects because the eyeball is too short. |
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What is long-sightedness (hyperopia)? |
The inability to focus on close objects because the eyeball is too long. |
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What can short-sighted people see? |
Close objects- such as book. |
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What can't short-sighted people see? |
Distant objects- such as children in a playground, are not clear. |
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What can long-sighted people see? |
A person who is long-sighted can see distant objects clearly, but has trouble focusing on close objects. They need to use glasses when reading or doing close work. |
