P5.3.2 - Lenses Flashcards

1
Q

What is the purpose of the lenses?

A

They refract light passing though them

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2
Q

What is the principal focus?

A

The point where lights parallel rays meet or appear to meet

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3
Q

What is the focal length?

A

The distance from the lens to the principal focus

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4
Q

The shorter the focal length…

A

The more powerful the lens

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5
Q

What is the purpose of the convex lens?

A

It makes parallel rays passing through it converge (focus) to a point

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6
Q

What is the purpose of the concave lens?

A

Makes parallel rays passing through it diverge (spread out)

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7
Q

What are the problems with short sightedness?

A
  • Eyes lens is too powerful
  • Eyes can only focus light rays from objects nearby
  • Eyes cannot focus light from objects far away onto retina, instead focusing rays in front of retina
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8
Q

What are the problems with long sightedness?

A
  • Eyes lens is too weak
  • Eyes can only focus light rays from objects far away
  • Eyes cannot focus light from objects nearby onto retina, instead focussing rays behind retina
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9
Q

What is a real image?

A

An image that is formed where light rays meet

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10
Q

What is a virtual image?

A

An image that is formed where light rays appear to come from

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11
Q

What does upright image mean?

A

Image is same way up as object

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12
Q

What does inverted image mean?

A

Image is upside down compared to object

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13
Q

What is the equation for magnification?

A

Image height / Object height

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14
Q

What are some uses of convex lens?

A

Magnifying glass, camera, eyes, projector, microscope, telescope

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15
Q

What are some uses of concave lens?

A

Spy holes in doors, back windows of coaches

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